Congratulations, and welcome!
My FI and I were engaged November 2011 and are having our wedding June 2013. We decided on working with a TA because we have guests from Canada and the US, and we wanted help to organize the dates and all of our guests (we are anticipating 60-80) . We are open to guests booking on their own if they so choose. We first went to a couple of different TA and we didn't feel a connection with two of them, but the third and final one is the TA we booked with. She is fantastic. She was able to phone and get a group rate early (usually prices are established 12-14 months in advance), but she took the extra step to phone the vendors to see what price range we would be looking at. When we first started looking at all the different resorts in travel magazines and brocheurs, it became overwhelming. They all seemed to blend together. We narrowed it down to one location (Riviera Maya, Mexico) and from that we made a wish list of 'must haves' and 'nice to have' at the resort. From that, we could narrow it down and selected a handful of resorts for our TA to phone and inquire about a quote. It took about two weeks to hear back the proposal. From there, we knew what we wanted to book. Since we booked the resort with the TA it has made things much easier. Hope this helps. Happy planning