The air museum at Wright Patterson AFB is interesting.

You have a lot of time. Why not go up through Canada? Niagra Falls, great lakes stop with camping etc.

What's a good place to stop for an overnight from DC to that area?

We are from Chicago and used to stop in Pittsburgh on our drives to/from DC. I actually live there now and there are a lot of museums if your kids are interested in art and science. You can also stop in Cleveland (2 hours from Pittsburgh for the Rock and Roll Hall of Fame) or Canton for the NFL Hall of Fame. Good suggestion of Notre Dame in IN but otherwise there isn't a lot to see in IN (IN natives can correct me if I am wrong). We usually zip through the state. Obviously tons to see in Chicago. Pretty boring drive from Chicago to Peoria (used to spend a lot of time for work in Peoria). I suggest you go to the AAA website or go to one of their offices and they can plan a route for you with stops on the way to Peoria and then up to 10 hours west. Have a fun trip!

Chicago, obviously. And the Indiana dunes are nice, if you are up that way.

If you like nature, the northern parts of Minnesota and Michigan have some beautiful spots.

If you are going to St. Louis, check out Cahokia Mounds. I went in high school and was really impressed.

We have to attend my husband's extended family reunion in Peioria, IL this summer. I will be driving there with our two teenage daughters (DH will be flying in/out for the weekend). We have between 2-3 weeks for the roundtrip. I am looking for nice/interesting stops along the way. Also willing to drive up to another 10 hours west if that will help people brainstorm. Thank you!