well, we went to aruba in october with all four.and we stayed in a timeshare on Eagle Beach *( case del mar). they had a fantastic kids program there. My oldest is 12.and youngest was 2. My 2 and 4 yr old did not do the kids program much. But my 2 yr old did go in there and watch a movie with her older brothers. they had scavenger hunts, bingo, pizza parties,etc. The pool was good for the kids too. I bought sand toys for the youngr ones & they spent lots of time, well covered in sunscreen playing on the beach....
Have you considered a timeshare? if not. check into La Cabana, Hyatt,places like that.Good luck