For Disney World, we bought umbrella strollers from the local Toys R Us even though the kids were 5. They are light and provide shade, and most importantly, they keep your kids from having to walk the length of the park which saves them a lot of energy which comes in handy when having to wait in long lines. And when they're not using it you can use it to roll your heavy stuff around. It made the whole thing so much easier for us every single day. And since they're so cheap you don't have to worry about people walking off with it, not like anyone would anyway.
I don't know if you're flying but another perk, when you leave, you may want to bring them on the plane with you as it gets you priority boarding. They get stowed by the crew and not in the main cabin anyway.
EDIT> I see you said your kids have a lot of energy, but it's a good tip for anyone in general.