TinkerLori,
A tent is allowed with any RV on a site (even the Premiums which are all concrete). To be clear, some folks try to sneak a popup (as a tent trailer) on a site with an RV or trailer. It is expressly not allowed (I have asked the direct question) but sometimes folks get away with it. I would not count on it.
But tents are a secondary structrure to an RV or trailer on all sites.
Of course, you are still subject to the 10 person per site limit.
Bama Ed
PS - in past years the descriptions of the campsites that WDW had on the Web explained this but the 2013 descriptions don't. Let's hope they go back to providing more detail.