You can go to disneygiftcard.com and combine them into one or two cards. You can have $1000 on each card - and it's much easier to hold onto one or two cards than a zillion. The crew member at Guest Services (and all those in line behind you) will appreciate it as well.
You can also combine them into one or two cards and call the number found under Gifts and Amenities up to 3 days before the cruise and buy OBC with those gift cards. Again, they will appreciate it if you have as few as possible.