We stayed in the park on the south end at Grant Village campground. I would highly recommend it. BUT there are no full hookups at that campground. We were fine dry camping and recharging the battery with the genny during the day. Stayed for 4 nights and used is as a base camp. I noticed that a lot of people only stayed one night but for us it worked well.
We drove through Fishing Bridge campground which does have full hookups but it was basically a parking lot of RV's. It may work fine for you but was not what we were looking for. At Grant village about half of the spots were pull through which worked well.
We came from the East through South Dakota and Wyoming, crossing the Big Horn Mts between Sheridan and Cody. Stayed at KOA's on the way out and back which served its purpose fine. (Kids loved the pools).
Feel free to contact me for any other info.
You will love the trip. I miss Yellowstone already after being home for a few days.
Our next outing is in a few weeks when we hit the North Shore of Superior for a long weekend. For those that have never been, put it on your list. It is beautiful anytime of year. Plan a stay at a Minnesota State Park North of Duluth, or Just South at Jay Cook, Once they re-open it after some bad flooding this spring.
2013S22BH/2015 f-150 ecoboost