Hi!
We were just at Disney in July and toured the Whitehall Room! We are using it for our Vow Renewal reception in December! I understand why you love it. My husband is an architect and I'm going back to school for Interior Design and we wanted something different than a "convention" room. The patio is awesome and the online videos I have seen of receptions in that room are really wonderful.
While we were looking at the Whitehall Room, I spoke to the GF Convention Center Coordinator about the setup of the room. We are only having 25, but I think you may be able to work it out. The dance floor is not large in that room but big enough for several people at a time. As you enter the room it will located on the left against the back wall. The cake goes on the table already setup under the mural. The tables can go on the sides and middle. You would only need 4-5 tables, plus your sweetheart table if you are doing it. If you do the sweetheart table, it goes in front of a pair of doors to the left of the patio entrance. Also, remember that you will have tables outside and that people will be going in and out. I don't think it will ever seem too small.
Another option you may have is at the Contemporary. One of the rooms, I can't remember what the name is, overlooks the Magic Kingdom and is large enough for 50 people. It does have a very "contemporary" look, but it is very nice. We are doing a Christmas theme so it didn't work for us, but if we were doing it at another time of year we definitely would consider it.
The other room that you might like the The Attic at the Boardwalk. We are having our Welcome Reception there. It is a much less formal room (with sofas, small tables, antiques, carousel horses, etc.), but is very charming and prettier than any venue I saw, including the Whitehall Room. The patio is very large and is covered/uncovered and overlooks Crescent Lake and the boardwalk.
I hope this helps out. Please email me if you have any questions or want to talk about Whitehall.
I hope