If you want to just park sort of near Navy Pier and leave your car for the day, the 146 bus runs from the museum campus up and down Michigan Ave. It will probably be filled with tourists on a summer weekend. Michigan Ave to Navy Pier is about 3/4 of a mile (or you can transfer to the 29 which takes you right to Navy Pier but if the weather is nice it's not worth it, IMO).
https://www.transitchicago.com/bus/146/
You can pay with the Ventra app