As said previously ... I think you'll need a bigger, different boat. I don't know of a cuddy that'll sleep 2 adults + 3 kids. You'd might, maybe get away with an express (mid-cabin) cruiser of that size but even then it would be too tight for my liking. Consider that you'd typically have 2 berths in a cruiser that size, each one sleeping 2 adults closely in a full-to-queen sized bed. Could you stick 3 kids in a berth ... maybe if they all get along and are the right ages / sexes (you didn't mention their ages). In a cuddy the head is usually a pull out porti-potty in the main cabin. In a cruiser you alway have a separate, doored (small) bathroom. On a rainy night you don't want to have to exit the cabin to go use the marina's facilities. I'm not sure what you'd do with dogs in either (cuddy or cruiser) case. You first need to find a dog friendly marina (wasn't there a recent thread on this ?) and then perhaps they could stay above deck, under the canvas if they're good (non-barkers) about such things.
One possibility that possibility that occurs to me is that perhaps a pontoon boat / cruiser hybrid might work for you. I've seen a couple of 'toons (? Sun Tracker ?) that had a "hard cabin" covering the aft 1/3 of the boat. I'm just guessing but I think that would be a separate, enclosed head as well as 1 berth and a galley. You get a lot of deck space (assuming full camper canvas) on a 'toon when compared to other boats of similar LOA and just maybe this is an option to consider. They're also less $$ to purchase. They are other 'toon owners that frequent the forum who can tell you how well such boats handle the lake. I can't speak from experience re: pontoons, we ended up with a mini-cruiser (24') ourselves. It's comfortable enough to overnight on, when we have guests at our mini-cabin or when we stay at a friends dock, but I wouldn't want to be spending a rainy week onboard.
Lastly, depending on how you define "affordable", an aft cabin cruiser like a Carver or Silverton would certainly work but I don't think they come quite that small. A larger express cruiser would also work spacewise.
Check out the boat dealer websites on the homepage links page. Silver Sands has both new and used boats listed, carries both express cruisers and aft cabin yachts. Not sure who carries what for pontoon boats.
EDIT: URL to recent post re: marinas and dogs
http://www.winnipesaukee.com/forums/...ead.php?t=2989