Will be traveling by car to Cleveland, OH from Boston in April to visit friends. Any tips for places of interest to stop along the way, and where to stay overnight? Also any "must see" things in the Cleveland area? 2 adults will be traveling with children aged 4,7,9 interested in sports, history, anything exciting and new! Thank you in advance!

You'll be going through Rochester. How about the National museum of Play? http://www.museumofplay.org/
They might enjoy Presque Isle State Park near Erie. There was a famous naval battle on Lake Erie. Any thought of seeing Niagara Falls?
Your kids might be a little young to visit the Rock & Roll Hall of Fame on the lakefront in Cleveland.

Look at US 20 which parallels I-90 thru a lot of beautiful country, tho this early in the year. Cooperstown, Seneca Falls, and Skaneateles are all interesting for various reasons. They are either on or near the highway.