I'd look into Sunsail or the Moorings. I think their prices for 40 ft cats during that timeframe would probably be pretty decent. You'll probably end up in BVIs since that's where most boats are, and its a good
family cruising ground because the hops between islands will be short. With very young kids on board short
sails seem best to me!
A
catamaran will be essential IMO, to have enough room for both
captain and your
family.
Maybe you could also do a week at the Bitter End Yacht Club in BVIs or some other family oriented full
service resort where you can get childcare and have some couple time? Both you and your wife, and the older kids, would be able to take
sailing lessons appropriate for your level, and they probably offer daycare for the little ones.