Hello, Canethia!
I've stayed at Disney's All-Star Music Resort for several years now, and it's a great resort!
You will be thrilled to know that there are splash areas in most parks, including Downtown Disney.
At Magic Kingdom, you can enjoy the newly-opened
Casey Jr. Splash 'N' Soak Station. I just checked it out two weeks ago, and can't wait to bring my kids back; little ones can spend quite some time there, and there's plenty of seating on the stone walls surrounding the area for parents to stay dry but close enough to keep the little ones in sight.
In Epcot, there are some great fountains that shoot up from the ground as you walk from Future World to the World Showcase. There are also some fountains like these near Mission Space and Test Track. Both of these will keep your family cool throughout the day.
At Animal Kingdom, we always plan a ride on Kali River Rapids ("you will get wet; you might get soaked!") just before the sun is at its peak, and there is a little fountain area near the bathrooms in Africa. These have helped keep my kids cool while in AK.
Finally, as you enter Dowtown Disney, at the Marketplace entrance, there is a little splash area where water shoots up from the pavement as well. If your kids need to cool off, this is a great area for them to do so.
Have a great trip to Walt Disney World! Send more questions as you think of them, too! We love to help!