We went the TA route as well. We cruised in 2009 for the first time, then cruise in 2010 and got engaged onboard the Carnival Liberty, and are set to get married on the Carnival Dream on April 28th, 2012
We had people pay deposits of $60 each at the very beginning just to hold their room, with full deposit of $250 per person due in order to confirm their room. Their full cruise price was due January 28th of this year and those were all done, then we booked a group flight again through our TA, a little more then what we were hoping to pay but there's no luggage fees and it's a DIRECT flight (thank goodness, just came back from a multiply delayed flight for work and realized my father would never stand for this lol).
Best of luck!