As I gather from your other posts on this subject, you are coming from PA via I-80 and you have reservations at Madison campground in Yellowstone.
Since coming in from Grand Teton NP is not doable because the south entrance will still be closed, I would recommend taking 191 from I-80 at Rock Springs. There is a KOA at Rock Springs and also Sweetwater Fairgrounds 307-352-6789. We've stayed at many fairgrounds during our travels and they're good for a short stay. You only need a one night stay there. Then take 191 to Alpine, WY and get on 26 to Idaho Falls and north on 20 to West Yellowstone and get to Madison campground from that entrance which will be open. Madison is the first Yellowstone campground you'll come to.
So...if you stay in Rock Springs or even if you see a RV park before coming to Rock Springs, stay there, then drive to Hwy 26 in Idaho and you have two options for staying just beyond Alpine, WY at Palisades. It's a beautiful area and you'll enjoy the scenery. It's a very easy drive from Rock Springs. You could also do a day trip to Jackson and stock up on groceries and fuel. Whatever you do, don't take Hwy 22 out of Jackson to Victor with your RV. It's very steep. If you want to return to Palisades via 22 from a day trip in your vehicle to Jackson it would be fine and scenic. Here are the two parks:
Palisades, Idaho RV parksFrom Palisades it's an easy drive to W. Yellowstone and Madison campground and again, very scenic. You'll pas by Upper and Lower Mesa Falls road around Ashton on ID20 if you want to check out them. You enter the half-loop off Hwy 20 - see the falls - and exit again on Hwy 20 - easy.