All the other suggestions plus any inexpensive Prindle 16 , nacra 5.0 or nacra 500 that you can find.

Interestingly enough almost any catamaran design will carry a family of four, there is alot of volume in both cat hulls. So that is never an issue except when you by a very small cat like the Hobie 14 or something.

Personally I would not go over 150 kg = 330 lbs as ready to sail weight. With each kg it gets harder to get the boat off the trailer and onto its beach wheel and to the waterline. For a long time I had a Prindle 16 myself (135 kg = 298 lbs) and it was one of the very best simple catamarans around for the use that you are looking for. It will carry 3 to 4 adults (been there plenty of times) so a family will not be a problem. It is one of the lightest "old designs" around and often get can be had dirt cheap. Rigging it is a breeze. And at 84 kg = 185 lbs I could right it alone with only a righting rope. It is very comparable to the H16 in many respects. But I has noticeable more difficulty righting the Hobie 16 singlehandedly. Either way having a righting bag on board is compulsory in my opinion.

I hear the nacra 5.0 and 500 are even somewhat better boats for this use then the Prindle 16 and Hobie 16.

Another suggestion would be the Dart 18 but these are very rare in USA.

Good luck.

Wouter