We stayed in West Yellowstone last August (2012) at Rustic Wagon RV Park. Rustic Wagon RV Park and campground with tenting and cabins,Yellowstone camping and lodging
Just wanted to have a smaller family owned park with a bit more privacy and without the crowds. (we visited Grizzly while we were there to also check it out) Another benefit is that I noticed there were folks able to arrive 'last minute' to 'wagon without reservations, so it is a good backup option. Grizzly RV park is most certainly nicer, but the sites at 'wagon were decent sized, less expensive, some are back in and some are pull-through, full hookups, a friendly staff, WiFi, cable, etc. and there is a good family restaurant next door. The trees shown are planted; there isn't much grass; the laundry and bathrooms are clean. Doing it again, I'd still consider 'wagon, but I'd also be quite happy with Grizzly.
Like you, we didn't bring a toad. Instead I saved on the fuel and vehicle stress of pulling our toad over several mountain passes and rented a compact car for $49 per day from a family owned rental shop in West Yellowstone that will both pick you up and drop you off right from your campsite. West Yellowstone Tours and Lodging- Steps from Yellowstone National Park
We found the rental to be VERY useful at Yellowstone. There were several places and wildlife we went to/saw that we otherwise would have missed due to parking issues.
We also stayed at Colter Bay in the Tetons and enjoyed that campground and the lake.
Tip: if you can get up early and enter the park early, you will have many more chances to see active wildlife and see the popular spots without the crowds. Most folks have the "hey - I'm on vacation" and don't enter the park until 11 or later and miss out on a lot! I did that on several days and it was well worth it. Photos are much better during the morning light anyway.
A bit of photos and route maps from our trip are here:Photo Albums