Linda:
The good news is that
Fort Wilderness has many sites that can accommodate a motorhome with dual slides, and all pads--no matter if it is Premium or just Full Hook-up--are level. The bad news is that I can't just give you one particular loop where every site would work because vegetation is different around every site. I have found that giving Disney a specific loop or site isn't the best way to go anyway to ensure that my needs are met. As much as their reservations department tries to make accommodations, some times they simply can't arrange a certain loop or site, especially when large groups want to come and all stay near each other.
I would suggest that when you make your reservation that you include all the information you've cited here: dual slides, room for an x-person tent, pet loop, etc. (I noticed that the last time I did online check-in 10 days in advance of my stay, I was allowed two "requests" like pet loop, a specific loop, water view, etc. but I do not recommend waiting until online check-in to make your requests.)
Our last site in loop 800 gave us plenty of space for a tent, and we were near the pet trail. I have found that requesting a woods view or an outer versus inner site in loops 700 to 1100 typically gives us a little more space for both slide outs, tents, and game set up like horseshoes. If all fails, though, and you are unhappy when you arrive at your site, Disney will allow you to change your site depending on availability.
Wishing y'all a magical vacation!
Whitney