The Napa room has a max of 50 and the Sonoma room has a max of 40. If you are trying to do a dinner reception these locations are great because you can see the MK fireworks. The Napa room looks directly at the MK. The Sonoma room faces the lake in the opposite direction but you can walk outside on the catwalks to see the fireworks. If you booked the Napa room you might be able to fit a dance floor in if you only have 30 people.
There is also a small fireplace room that is part of Victoria and Alberts which is great for dinner - but I fear that 30 might be too many for the location. I am not sure what the max is.
Depending on your theme there are a bunch of other more obscure locations like the Beauty and the Beast stage at MGM that has a max of 50.
I guess it really depends on whether you are looking for a typical reception reception or whether you want something a bit more unusual.
Thank you everyone. It looks like we decided on the Attic. Df was hesitant because he didn't want a brunch but after much deliberation last night we settled on France and the Attic!!