Without knowing details about the car and exact addresses, I went with EV Trip Planner on a Model S with 21" rims from Lima to Sandusky and back, with a cabin temp of 70, 500 pounds of passengers, and 30 degrees outside. 72.7 kWh / 249 rated miles round trip, give or take for exact addresses. If you have an S60-S75, I'd plan on making a detour. With an 85-100, you're probably fine, but might want to make dinner plans for the ride home near a destination charger.
If it were me, I'd just plan on a quick trip to a destination charger to plug in temporarily after the water park. Drop the family off at the hotel and drive over to the Motel 6 in Milan, it's five miles away. Plug in until someone asks you what you're doing. They have four (!) destination chargers there at 16kWh, so something will be available and it shouldn't take long to hit a comfortable level.