Congratulations and have fun with the A frame! It is cozy and very glad you're not having any leaking. I bet the Tetons were wonderful and Jackson Lake is thawed out.
I like the Yellowstone campgrounds but I have not stayed at all of them.
My favorite is Tower Fall but it was closed through much of my trip this year. Though it doesn't designate at ok for trailers, once you get past the first part of the entrance road I think it would be ok. The location gives you great access to the two main wildlife areas. There's a good chance you'll get bears wandering through the site and will hear wolves howling at night.
I also love Madison campground. The setting is great and it's in a good location. But, it is a bit far off from the traditional wildlife areas (though there have been some spectacular wildlife opportunities on the west side of the park so far this year) . If you're into thermals, it's probably the best location with fairly quick access to Old Faithful, Grand Prismatic and Artists Paint Pots. There are plenty of pull through spaces and it has a water filling station (but no hookups).
Norris is a very nice campground as well that does have spaces that easily fit the A frame. It is very centrally located and also right on the Gibbon river if you want to fish (it was severly overflowing while I was there). Again, no hookups.
Mammoth is nice as well but it is right next to the North entrance road so it gets busy and it's in a more arid environment and I prefer the pines. Still, it's nice. No hookups here either but plenty of pull through sites.
Fishing Bridge RV park, which I've never stayed at, does have hookups. It is pretty far off on the east side but still not a bad location.
At this time of year you really want to get to a campground as early as possible as they fill up quickly.