I voted for croquet, but only because that is what we have, and DH and I spent many evenings out playing that in our yard last year (also *ahem* mature and childless, btw). I got our set at LL Bean for $99, and it is very good quality.

That said, I am itching for a bocce set now too. This is a really fun game, especially with a margarita or two

SheFly