I am thinking about booking a 7 day Eastern Carribean cruise somewhere in the time frame of next January through April. I want to make sure it will be warm enough for my 2 DS (ages 3 and 4) to swim in the pools on the ship and at the beaches at Castaway Cay, St. Maarten, etc. Is it always warm enough for that in Jan./Feb. or would we be better off to wait until April to make sure we get warm weather?