There is also a place that has a Wendy's, Pizza Hut and KFC that has an inside playground at Exit 108 on the corner of Man-O-War and Pleasant Ridge by the Chick-Fil-A mentioned above. I don't thing the food is that good, but the play area is larger. The park mentioned is very nice too.
Jacobson Park has a very nice playground. You take the Athens-Boonesboro exit, which is the one just south of exit 108 (Man-O-War.) Jacobson is maybe 2-3 miles towards town on the right. It is probably about the 2nd light away from the interstate. If you use that one, tuen left as you enter the park. The road will loop around and I am sure you will see the play ground since it looks like an giant log fort. There is a Wendy's, Hardee's and I think a McDonald's at that exit. Gas stations too. This one may be the easiest since there isn't a lot of traffic out there. It would just mean the playground is outside and it will be cold.