I just went to a wedding at Mayfair and do not recommend its food, the food was BAD.
I went to a rehersal dinner at Perricones. Beautiful setting, you would probably rent out the entire patio with that number and the food was quite good considering the size of the group. Also, the service was very attentive.
As for others near Brickell:
Cafe Sambal at the Mandarin Oriental is a beautiful setting and the food is usually pretty good (esp the burger!). They have japanese/asian style food.
I think a fab spot for a rehersal, if your willing to go to SOBE, is the upstairs room at smith and wollenski, its Beautiful and overlooks the bay and the food is surprisingly good for an old school steak house (its one of the spots I have in mind when my time comes ;)
EOS is an awesome setting (great decor) w decent food but may be expensive
Balans opened on brickell, i havent been yet but the one on sobe is pretty good
There is a Capital Grill on Brickell, nice setting, good standard steak house food
Once upon a time i had a good meal at Dolores But You can Call Me Lolita near mary brickell village, i looooved the decor (in the old firehouse, white walls, candle lit), but not sure how the food is currently
River Oyster Bar (again, havent been in a long time, but used to love the food). Not fancy, next door to Tobacco Road which is an old Miami bar (fun spot to go post dinner for guests looking to stay out).
If youre willing to stray off brickell you'd def find better restaurants, but I think the above mentioed are some of the best bets for that general area.
65 is a pretty big size, not a lot of stand-alone restaurants that could handle that kind of group. You may want to look at Gibraltar in Grove Isle which is one of the few places that jump to mind that would have the right setup to accomodate that kind of group. They only recently took it over and I've not been yet.
Most of the hotels likely would have banquet rooms, but it's not always easy to judge what you'd get in the way of banquet food based on what the hotel restaurant is like.
You may want to look into buying out Andu for the night. We had a cocktail reception there a couple years ago that they did a great job with.
If you're willing to head off the mainland and over to South Beach, Talula's outdoor patio might be able to handle a group of that size.
I recently went to a rehearsal dinner at the Mayfair hotel in the Grove and it was really nice. They set up tables outside, since the Mayfair has this indoor/outdoor feel. The food was pretty good, but what was really nice was the atmosphere. They also set up an area with couches and chairs, like a lounge space. The rehearsal was at St. Jude in Brickell, so the Mayfair is only about 10-15 minutes away.