Hi juanitaeagle! I'm getting married at Aventura on December 10, 2011, so your wedding is obviously before mine. So I am in no way speaking from experience, but rather from things I have learned from other BDW girls!
As far as flowers, it seems like you pick these when you get down there and meet with the wedding coordinator. Then she can show you pictures in person. Also, I believe the flowers depend on availability and the season, so you never know what you may be able to get or not.
For the restaurant, it seems that alot of people go with Mundaca (the steakhouse, but it's on the Cove side). I have heard it has an outside terrace that is perfect for smaller wedding parties and it offers more privacy. Several people have said Mundaca was their favorite restaurant on the Cove side...I'm not sure about the Spa side.
For music, we are considering getting the harpist for the ceremony and Mexican trio band for the cocktail hour. They are a bit pricey, but I have heard it's worth it and people really enjoyed it. Although, one girl had a negative review on the harpist because she didn't play traditional wedding music like they had asked. I personally just don't feel like dealing with an Ipod and bringing my own music...many people have done this though!
We too will just be having dinner in one of the restaurants. We'll probably have about the same number of wedding guests as you...around 20 or so. I just couldn't fathom paying for a private reception and DJ for that small number of people, especially when we are at an all-inclusive resort to begin with. I'm hoping to have a nice, long dinner and then entertain ourselves until the resort disco opens (I believe it's open from 10pm-2am).
Does anyone know what time the specialty restaurants open at the resort? Is it 6pm?? I'm trying pick a ceremony time so that the events kind of flow together and are not spaced out. I already picked 2pm, but I'm hoping to change it to 3pm!