Hi there, am looking for something similar to you after rediscovering the delights of little cat sailing after a long hiatus. The boat I played on last weekend was a Calypso 16 which satisfied my adrenalin needs just fine.
My mentor - who, having taught me to sail when I was a kid and should, therefore, take full responsibility for the crazy sailing junkie I have become over the years, provided said Calypso toy to play on. This is the sound advice he gave for buying a cat to just have some fun on...factor in, I have littlies...so tweak, for your requirements.
Avoid Hobies, they're a bit tender and tippy.
Avoid centreboards/daggerboards - more things to think about/look after.
16ft is good - little extra length to spread out.
Mari, Windrush, Calypso
I partially agree with BlueMoon...I wouldn't go to 18ft...but 16ft was okay for me 60kg with two featherweight littlies in a steady 15ish breeze. Bordering on out of control gybing (because she wouldn't tack in the short sharp chop) but I didn't kill the kids and we made it back to shore without capsizing lol...it's all part of the adventure!

Happy hunting!!!!