Liveaboard/cruising Cats w/kids

[pangaea6]

I'm thinking of living-aboard/cruising with wife and 4 kids (under 10). Would like to do the east coast,Caribbean/and cross the Atlantic to Med. Any Rec. on which cats I should be looking at and how old of a boat can I get away with? I've been reading lots of message boards so now I'm looking to get feedback. I think cats would offer a little more room and safety and ease of sailing compared to monohull and cheaper in the gas dept. I've never sailed so all the advice is welcomed. Looking for something under $400k at most but could go $500.