Philly PA to Chicago to west Yellowstone.
 

So our family has decided to do a 2 week road trip to Yellowstone end of June. 4 adults and a 1,4 and 13 yo. Youngest daughter and I are flying into PA Friday night and my other daughter and her family are picking us up. The plan is to drive thru the night to Chicago since there are 4 drivers. Booked rooms in Chicago for Saturday night as we all want to go to Navy pier and see the Cloud aka the bean...lol then from there we would like tips and info...on our list of what we want to see Badlands, Devils Towers and Mt Rushmore. We are scheduled to check into our KOA West Yellowstone on Tuesday and we've got 7 days camping and doing Yellowstone, before we have to head back to PA to catch our flight home to the real world of the working.....Any tips to add fun for the kids......

Why not just fly home from either of the Chicago airports and save a long drive across Indiana, Ohio and how much of PA? Philadelphia or Pittsburgh?
Whatever you save by flying to PA will be eaten by gas fillups even if you don't have a drop fee.

For the trip home you might consider adding a day and heading down to Colter Bay or Moran and see a bit of the Tetons before heading back to PA.

My oldest daughter and her family live in Philly. And we all want to be together for the road trip and that is where the road trip starts lol. We all actually like being together.