I though of Hersey Park, but that is more of a weekend thing, really looking for a place that is truly geared for kids. This is why I originally planned WDW because there is no place in the world that is as child friendly as there. Thinking more along the lines of say "Atlantis" in Bahamas, or Sandals, anyone every been in either? Another problem is he will just be turning 3 that month so he will not really be old enough to go to the kids activities.
We did FDR Pebbles, which is geared toward families, in Jamaica with our 2-year-old. There are others like it. They have activities for the youngest of kids, and each room comes with a built-in nanny to help take care of the little one. It was the first time we ever did one of these all-inclusive vacations. The place was beautiful, and there was nothing wrong with it, but to me it's a bit like hell, and I will never again do that again. But we are independent travelers who prefer the thrill of discovery on our own.
We much preferred going to a place like the Goblin Hill Villas in Port Antonio, Jamaica. Each room comes with a maid who will cook and clean for you, but after that you are on your own to discover Jamaica. I am sure you can google them. But if you prefer an all-inclusive with everything planned for you, then FDR Pebbles (and the like), await your money.
PS, if you can afford an all-inclusive in the Caribbean, then maybe you can rent a condo in Mammoth Lakes, California. It's in the Eastern Sierra Nevadas, where the granite and water of the highest peaks in the country drop down dramatically to a high desert plateau. The scenery of Mono Lake, Lone Pine, etc is stunning. You can hike, search for pictographs, take a bath in warm springs, admire a bristlecone pine forest (the oldest living things on the planet). I think this is the most beautiful are of the US.
Or rent a home in the Adirondacks for a week. Garnet Hill Lodge has regular lodge rooms as well as many nice homes for rent. There is all manner of activities nearby, including a beach on a wilderness lake. Lake beaches, with no waves, can be less frightening to toddlers.
othe rideas where you can rent a place for a week: the Finger Lakes in NY, Cook State Forest in PA.
And if you really want to go to amusement parks, the best ones are the historic parks in PA like Knoebels.