I think some parts of Disney are great for little kids, but it also can be overwhelming. Waiting in line can be stressful for impatient kids, and it's awfully hot if this is a summer plan you are talking about. If you spend the money on a park pass, and then he's exhausted after a few hours, will you feel you need to stick it out to get your money's worth? The hotels often have pools as well as kiddie activities, and certainly the transportation back and forth is well done. If you're in the area and want to do Sea World on a different day, that's fun too. We loved it for our kids but found it better from age 6 up. A few rides/attractions are boring for 9 and up, but there is plenty more that they can do that the little ones are too scared by or to short to ride on, so it balances out.
One thing we enjoyed so much was a beach vacation. Have you considered a place like Cape Cod or the Jersey Shore? We always went to Cape Cod because there are 3 levels of beaches -the bay side with the warmest water and no waves, the Nantucket Sound side with mild surf, and the ocean side with big surf and cold water. Flying to Boston or Providence and then renting a car is very manageable.
We have rented cottages so we had a kitchen and a place to just crash, and we have also stayed in hotels with a morning kids' program, so my husband and I could get a break too, lingering over coffee while our son ran around with "camp counselors" and other kids, looking for shells on the beach or being on the playground, or playing other games. Then we still had the afternoon together. There are a number of places right on the water - some with hotels, some with condo apartments, some with cottages - so there's no driving necessary. They also offer babysitting and a children's dinner program so my husband and I could get a dinner out once or twice, just the two of us.
Seashore vacations might be a nice thing to do - to show your child the ocean - and also have some down time on the beach. You can rent all the stuff you need (umbrellas, etc.) and usually when we've rented a house, the owner includes beach chairs, beach towels, umbrellas, and so on.
On Cape Cod (where I've taken many vacations), and also on the Jersey Shore (where I have taken a handful of vacations - but check for SuperStorm Sandy damage) there are amusement parks, bumper cars, go-karts, trampoline bouncy places, and so on. Cape Cod has a number of things to do on a rainy day - small and manageable museums (natural history, small aquarium, fire engine museum, hands-on kiddie places), public library programs, and more.
What I like about these places is you can just have fun on the beach instead of an entirely orchestrated vacation of events and rides and lines to stand in, but there are still lots of things you can choose from if you want to.
Have fun deciding!