Some more tips for your trip. From Disney to Marathon you have at least a 5 ½ hour drive south one way. Round trip that’s at least 11 hours lost to driving instead of having fun.
An alternate suggestion would be to seek out places to kayak and have fun with the kids on the way back home. We’ve found state parks to provide the best memories for less money.
In addition to Sarasota there’s a lot of places to take the kids for kayaking, etc. that won’t take you out of the way on long drives plus will give your wallet a break from Disney’s prices too.
On the way back north from Disney you can swing northwest over to Crystal River for swimming and kayaking with the manatees. Kids love that and it makes for great memories. In fact our grandkids loved doing that better than Disney and treasure their photos of swimming with manatees. Keep in mind these are a protected species so it may be pricey. We did it with our grandkids and the memories were worth every penny. Here’s more info
How to Swim with Manatees
https://www.visitflorida.com/en-us/things-to-do/outdoors-nature/how-to-swim-with-manatees-in-crystal-river.html https://swimmingwiththemanatees.com/ https://crystalrivermanatees.com/Some other places to visit with good activities for kids plus your water activities are the state parks in Georgia. You can RV camp and do your favorite things. It’s a good value for the money.
Crooked River SP at St. Mary’s, GA
https://gastateparks.org/CrookedRiverStephen C. Foster SP at Fargo, GA
https://gastateparks.org/StephenCFoster. Our grandkids loved the swamp tours and had bragging rights with their photos of alligators.
Further north you have Ft. McAllister SP just outside of Savannah. They offer historic re-enactments that kids love plus your water activities.
https://gastateparks.org/FortMcAllisterHere is an interactive map of Georgia State Parks
https://gastateparks.org/Map. It helps us to find state parks along our routes when traveling.