Ok, I have lived aboard with kids and two dogs. I made somewhat of the same plunge, but will give you my experience(s). They are very opinionated, but have been there and done that. Of interest (I hope) to you is that we are soon to do again, hopefully.
Now, here goes:
#1) 15g holding tank will not last long at all. I think ours was 25-30g for me and Kris and we could go through that easily in a week. Chase was in diapers. So add another user in (who probably will not flush economically), and I sincerely doubt you will make a week. And remember, you don't get the full 15 gallons. We always try to stop and pump out when ours is about 80% full. Because if you over pump and get poop/tp in the vent tube from the head, it is a absolute nightmare. In essense, I would add a blader or something to get to an easy 25-30g's of holding.
#2) The dog will be a major PITA. MAJOR. And you better make sure he/she can go up and down the steps on their own and get off the boat on their own. The dog, of everythign you have mentioned (except maybe the baot) will be the biggest headache. Sorry, it's true. Go check out the many cruising/LA with dog threads here. And let's also remember that even though that dog may be able to get on/off now... if they cannot in the future you are in for big trouble or may have to put the dog down early. We can discuss this in legth if you want, but between that and taking it out 2-3 times day and the sever restrictions on pets in even many marinas, and where they are going to go to the john when it is raining, icing or snowing, the ability to get on/off the boat and the dink, and the fact that most countries do not want them in their territorial waters (much less their shores) - you are in for an eye opener. Research this matter heavily. We ended up getting another dog, but I honestly regret it. I am pretty sure she will have to find another home before we get seriously cruising. And we have not even mentioned whether that dog will get sea sick. You won't know till you are out there. Research this heavily and use your heart AND YOUR HEAD in making the final decision.
#3) We use a small wet/dry vac which is close to a mandatory on a LA boat. You will have to run generator or large inverter to power.
# 4) We have not lived aboard in the cold climate, but the current boat is in a lake and it get quite cold for us in the winter (below freezing). We use both the R/C air cond and heating, and a lot of space heaters. Your best bet though is probably getting a propane heater in liu of the r/c system in my opinio nas it will probably be more efficient and I would assume much cheaper to run especially in cold water. I think when the water temp is around 45-50 the r/c systems become very inefficient or may not hardly work at all. Space heaters are very inefficient and burn lot sof electricity. Also, they require a generator. You cannot run that all day on teh hook unless you are made of money and diesel. Forget the wood burning thing. This is a boat not a house.
#5) A Kettenburg 40'?? What in the world led you to that boat? No freaking way I would EVER consider an old wooden boat for my family of anything I was serious about. You need fiberglass or steel or something other than wood. We had this wooden boat in our marina that was always leaking (they all do). That thing was always trying to sink (they all do). It almost became a joke every morning on who got to call into the marina to pull out the pumps to keep her from hitting bottom. And if you get a wooden boat from FL where the water is salty and move to a brackish or low salt environment, that thing better have a bunch of bilge pumps!!! Forget the wooden boat idea. Avoid wood like the plague. Even concrete is better than some old wooden relic. The exception to this rule is a very well cared for wooden boat (when you get it) and you have lots of money. I must assume that one or both of these conditions is not you???
#6) If money is less of an object, get a LCD flat screen and bulkhead mount. We have one and it is better than watching on the lap top. If money is a bit more of an object, then just use the lap top. Unlike many others here, I am not opposed to TV (though we only watch movies in general and even then very little). However, it is nice to watch the weather before storms with the TV and hey... this is your home not a weekend getaway. Still, you will have a million things to spend money on and make sure the TV and sound system is very low on your priority list.
#7) Living on a mooring, in a cold climate, with a kid, dog, and a wife that has to go to work (or both of you going to work) is an absolute recipe for disaster. DOn't screw up what can be a great lifestyle. I know people that have made that work (without the cold weather... this is in S FL), but they are few and far between. Still, even they did not have a dog. You need a marina. In my opinion, unless everyone is made of tougher stuff than any LA (live aboard) I have ever heard of, you will burn out on that boat within a few months. Maybe weeks. Then you are broke, stuck on a boat, and liable for all the associated costs and frustrations of getting OUT of the lifestyle that you have locked yourself into. Remember, buying a boat is like buying a large piece of land in the country. It is a wonderful experience at first. Buying it is easy. But getting rid of it can be a very long and financially draining process.
#8) On the toolkit question: I have a full complement of hand tools (screw drivers of many lengths/sizes, 1/2 and 3/8 driver set in metric and american), a drill (both battery and electric but I have a large generator and inverter), a dremmel, a heat gun (for heat shrink), and a Jig Saw. With the jig saw, you can probably do anything you could do with many other tools - including a circular. I do not think a circular is necessary. It is nice, but not neccesary. The jig can do it all. And it is imporatnt to remember that space is a premium on a boat and you need to minimize your tools too for those that can use multi-purposes.
#9) I personally (and especially with a dog and kid and wife that works) NEVER get a dink without an engine.First time you gotta take that dog to take a crap in a rainstorm or the middle of the night in a blow and you will either be buying an engine or ditching the dog. And I believe that with a child, you need a way to get that child quickly to emergency services. Seconds last for hours when on a boat with a hurt or sick kiddo. Their safety takes precedence to ANYTHING and EVERYTHING you do.
#10) I do not want to start another gun debate, but just leave the guns at home. You should have a 12ga and probably a 25mm flare gun that would easily kill in close range. And on a boat you will be in close range. There are no 'Pirates of the Potomic' so at worst you will have some nut job board you in the middle of the night. But the odds of this happening are astronmically small. Your flare gun should be fine.
As far as the rest, I can get you one of the best surveyors I have ever known in FL. That's not an issue.
You are doing the same thing many of us have done - but you will find most have not done it with kids. Kids make it MUCH harder (and more enjoyable). But it does change the rules. We are here to help. Ask questions as you wish.
Here's some LA and sailing pics:
Mom with my oldest (at that time):
My wife and oldest son:
Chase watching TV (on a computer, incidentally... we used the computer at that time as flat screens were not an option)
One of our dogs:
The kids today: