That sounds like a wonderful trip.... the past several years we have stayed in cabins and cottages in the areas that we have visited and have been totally happy with the accommodations. Several of the places have daily maid service and the linens are supplied. When renting an RV the linens are often not included.... so you need to think about that.. Here is a link to a place that is very close to Yellowstone and looks great..
http://faithfulstreetinn.com/
I have no affiliation with this lodging facility - it looks like a place that I would consider - we are planning a trip to that area in the next couple of years so I was in the process of checking out the various options for our visit to the area. If you do an online search for lodging in the area of Yelowstone Park you can check out other possibilities.
Good luck in your search.
Sue in PA