We are currently equipping a boat for long-term (five years, we hope) cruising and we face these questions every day. Capacity isn't so much an issue as it's a steel full-keeler of some 40 feet on deck, 42 LOA. We are going for some complexity in the energy-self-sufficiency department because we'll have a child aboard, and I write for a living, necessitating some way to stay in touch offshore to run in a minor way my business and to transmit and receive educational materials for our kid.
We will also be renting out the house as two flats, and while I will assign to a manager the general landlording duties, I will have to approve expeditures, file house taxes, monitor utilities, etc.
Generally, we are moving into a fairly rarefied subset of cruisers: the anchoring-out, lone wolf types, and the equipment list is reflecting this.
Stuff we won't have: Air conditioning on the hook, a diesel genset, a fully electric windlass, a RIB, a 9.9 HP outboard, cockpit lockers, huge alternators, bow thrusters, electric winches, davits, two heads, dedicated nav displays, satphone.
Stuff we will have/already have: Espar heating for offshore, Mermaid A/C plus heat if we are on shore power; a Honda gas genset, a custom arch for comms, shade and 3 or 4 large solar panels; 4 x 8D AGMs; wind generator that can be towed, like a Duo-Gen; two tenders (Portabote and nesting dinghy) stowed on deck; small workshop forward; 2000 W inverter/charger; foot pumps for water; only one head; PC-based nav display; extensive fuel filtering, a separate polish tank; new water tanks; manual-optional windlass; four anchors; multiple rodes; feathering prop, large inventory of spares.
The idea is to stay independent of the shore when desirable in order to reduce costs. I don't object to tying up in a marina now and then, but it runs counter to our ideals of self-sufficient cruising. I would rather get more months of zero-sum cruising (the house rental will pay down the mortgage, the utilities and probably my diesel bills, and I can afford $25K/year for our trip, which is plenty if I'm not eating ashore every night) than to have a gold-plated trip. We may haul out for a season in New Zealand to put our boy in school and do maintenance halfway through our trip.
Beth Leonard's "Voyager's Handbook" is very good at laying out the different styles of cruising: the totally budget "do it now with what you've got" idea all the way to the high-life style found in the Caribbean. Our boat, and our plans, are more "Ocean Navigator" oriented, because we intend to go off the beaten track a little farther...we haven't ruled out high-latitude sailing as the boat is built for it.
Anyway, that's where we are now: making complex adjustments in order to have a simple life aboard.
The advantage of a forty footer is (a) more room for crew. (b) Longer on the waterline = faster = shorter passages. Guard against the temptation to drag along too much stuff. Given that you have offspring to bring along, it makes sense.
Heating: A bigger boat requires more complex and therefore more vulnerable to failure, systems. Bring lots of warm clothes. WE find that a single burner Origo alcohol heater does us just fine. WE use a 5200 BTU electric heater from West Marine while plugged in at the dock. Another advantage of a small boat.
Solar panels, wind generator: you'll need them at sea and on the hook. Gas gensets=Bad. annoy everybody.
Fuel system: Possibly unnecessary complications. (But I could be wrong)
PC Based navigation: Good for planning, otherwise - Bad. Prone to failure and may give false sense of security. be sure you have complete, up-to-date paper charts and plotting tools and know how to use them. Also have at least one hand held GPS with plenty of spare batteries. Disclosure: I have Garmin software and GPS interface on my PC but I NEVER use it for navigation while under way.
While I'm on a roll (Or rant as it were); Navigation necessities, In my opinion of course, are:
Good quality steering compass.
Another good quality steering compass.
Two or more hand held GPS units. These don't have to be fancy as long as they give you the basic data - lat, long, speed. We have one Garmin GPS76 and two GPS 38s. Total cost about $400. You MUST (In my opinion) have GPS unit(s) that operate independently of the ship's power supply and not too fancy lest yo be tempted to forego real charts.
Depth sounder. Even a lead line. A necessity when anchoring and very helpful when you are sailng where you shouldn't be
Current NOAA or Admiralty paper charts. Expensive but no prudent navigator would think of going to sea without them.
Plotting tools. I use a Jeppeson aviation style rotating plotter/protractor and a Field Artillery plotting square, a 18" steel ruler and a set of traditional brass dividers. #4 pencils don't smear like #2s do. These work for me because I'm used to them and know how to use them. (My life story can come later) I don't like parallel rulers or yachtman's plotters but you might find they suit you. Use what works for you but be damned sure you know how to use the tools that you choose.
Tide and current tables. Paper, not on your laptop. (Again, electronic is OK for planning but it is not a substitute for a book printed on paper)
Good quality binoculars. 7X50
Hand bearing compass.
A good stong hand held spotlight with it's own battery, not one that depends on the ships power.
Log. A device that tells you your speed through the water. Record speed, time and compass heading in your Logbook or deck log at regular intervals to determine your DR position.
Chronometer. Really a good wristwatch will do and I don't mean a Rolex. We each have a Rolex and neither of them keep good enough time for navigation. Any decent quartz watch will be superior. If it has a stopwatch function so much the better.
Logbook. To record our position fixes to facilitate dead (Or ded) reckoning.
Any additional information about your cruising grounds you can get. Charlie's Charts, Wagonners, Yachtsman's chart books, whatever.
Sextant. Eh... not so much. For the price of one cheap sextant you can buy two cheap GPS units that will be far more accurate than any position you can get with a sextant from the deck of a small boat, and by "Small boat" I mean anything under 200 feet on deck. (On Endeavour, 151 ft LOA, the best I could do was a cocked hat ten miles across. My GPS 76 typically gives a position within one boatlength of my Vega27) Bear in mind also that, on our recent Pacific crossing we did not see the sun, let alone moon or stars, for five weeks. Sextant's no good under those conditions Buckwheat. Then there are the tables and almanac you will need along with the sextant. Skip the sextant and buy three handheld GPS units and plenty of batteries with the money you save. Keep a log and fall back on DR in the unlikely event that all three of your GPS units fail.
OK, I admit I have a sextant, and HO 249 and almanac. Mostly I use the sextant turned sideways to take bearings for coastal navigation. Then check my position plot with the GPS.
Whoops! Looks like I got off on a tangent there. Sorry I just thought I had something to say and my fingers went off on their own. Not aimed at anyone in particular you understand. Well, not after I got started on navigation anyway. It's just that I have strong feelings about computer based navigation. All well and good until the batteries go flat or the salt spray gets into the works then it's a dark and stormy night and the laptop won't reboot and that's when the screaming starts. And it's "My mother warned me not to go to sea!", and "What do you MEAN you don't have a satelite phone?!?!?!?" and then it's "What'll we DOOOoooooooooooo!!!!!!!?!?!?!? and that's when the cat stars wailing and throwing up in your slippers.
Now, If it was me, I would calmly light up a cigar (Punch double corona, maduro, of course), fire up my number two or three GPS unit, verify my DR plot on my paper chart and authoritatively say "Bring in the Jenny and hoist the number 2 jib. Take another reef in the main and lay 'er on the starboard tack at 040."
But that's just me.
Malie ke kai