Often times TA's can negotiate a better group rate/room block with your resort. In addition, we have access to different airfares and booking engines that you don't have access to - and can often get very competitive airfares.
In addition, we are your stress reliever! Instead of you having to deal with questions from your guests, tracking your guest's bookings, general travel questions, etc. in addition to all of your wedding plans, you can direct your guests to contact your TA with any questions, etc. they may have.
There are several TA's on here - I am the Canadian TA - but I would recommend contacting Tammy(host) and she'll be able to help point you in the right direction!
Lindsay