I'll second the vote for a Catalina 25. A member of the YC recently had one and i've been aboard a few times.
I was impressed with the setup and can imagine 4 aboard for overnight.
A Good plan, Starting small with a trailerable boat will keep it fun, cheap and give you the range (behind a car) to explore lots of cool areas and lakes. Just learn how to reef and read a forcast and don't scare your wife and kids by sailing like a maniac and you'll be right.