A couple of options...
You can combine Disney GCs up to $1000 into one card. Then you can give the TA that card number. Much easier than before when I would have stacks of $50 cards.
Or, you can signup for a Disney Vacation Account. If you have (or will have) $1000 in Disney Gift Cards, then you get a free $20 for every 1K. So it's a little extra money. You deposit the GCs and then when you are ready to make your final payment, you will call a special number and they'll apply the balance on the account towards your cruise payment. The account is free, but you need to have it open for at least 120 days to get the GC.