I thought I gave my answer in another of your posts but can't find it.
If you're coming in from I-80 and since the south entrance to Teton will still be closed, I would recommend that you get off I-80 at Rock Springs and take 191/89 to Alpine, WY then pick up Idaho Hwy 26 to Idaho Falls and north on 20 to West Yellowstone and east to Madison campground. It's a very beautiful easy drive with a RV.
When you leave Madison leave via the south entrance into Grand Teton Nat'l Park. I hope you don't pass up Grand Teton. It's altogether different in looks and things to do than Yellowstone. If you wanted to explore Cody, WY from your Madison stay you could easily do that as a day trip.