Whitney,
You can have up to 10 people per site (you will have to list each name and age on reservation). Tents and small trailers can go on any of the four site types but there are some inconveniences in some combinations. Premiums are all concrete as you say, 18 ft wide paved and over 50 ft deep. There is no tent/sand pad but tents can go on the concrete if you want BUT YOU NEED TO KNOW that there is no sand pad. Some folks have the round self-supporting dome-style tents that will manage on concrete but they can't be staked down obviously.
On the Tent sites, a small trailer can go on them BUT YOU NEED TO KNOW that there is no sewer hookup. They are 12 ft wide paved and about 35 ft deep paved and have a sand/tent pad of varying sizes behind the pavement. The Preferred and Full have the sand pad and sewer hook-ups and differ only in their location in the Fort.
So you could do a Tent site if you can get by without a sewer hookup as the cheapest way to stay at the Fort. Of the two Tent loops, 1500 is closer to the pool central area but 2000 has bigger tent pads and is further away from the main pool area. But then again, if you have golf carts, distance is not so much an issue.
In any event, make sure to designate you will have both a tent and trailer on your reservation. If your tent is bigger than 12 ft in any way (length or width), add the dimensions to the reservation by phone. And the size of the trailer. Campsites are automatically assigned but if you provide the vital info it may get caught and the CM will ensure both units will fit in whatever site they assign to you.
Here is a Tent site in 1500 (with turkeys crossing):
Here is a Preferred site in 200 with a tent:
Here is a Tent site in 2000. Note the sand pad has a little extension for the picnic table so a bigger tent can be placed in the main sand rectangle.
Here is a Premium site in 800 with a tent. Note it looks a little awkward.
Bama Ed