L124C has a great point- here in Hawaii it's much easier to live aboard a small boat as the weather usually gives you all that additional deck space to be on- my neighbors across the dock have 3 kids under the age of 6 and live aboard a 30 ft custom gaff rigged wooden sail boat-They're experienced sailors and feel they have plenty of room now (of course when those boys get to be teenagers all bets are off lol!)
When my husband and I were looking for our boat I was overly concerned with length and over the years came to realize that it has nothing really to do with whether the boat is a great liveaboard or not.
(I used to be like the guy in "Jaws"... "We need a bigger boat...")
Look in a range and don't rule out those 27 footers...
Author & Sailor