Bentley Brook which is attached to Jiminy Peak has a mountain adventure park. The price isn’t included but it is very fun for kids and you can walk there from the resort. In the winter there is skiing. We were very impressed with the activities program for kids. There was a lot of stuff going on all day. There is also a horseback riding place not to far that is kid friendly.
Pigeon Forge Tennessee has a lot in the area even if you don’t stay at the water park. Crystal caves, aquarium, theme park, hiking and more.
The Williamsburg area is always a lot of fun. You can get inexpensive fun cards for the parks.
National Harbour has the giant Ferris wheel and a carousel. The Gaylord is right there and has events often.
Rhode Island has beaches, cliff walk, great places to fly kites, and tons of playgrounds.
It really depends on what you like to do. My kids are fine as long as they have a pool.