FIrst off, Welcome to the Forum! I am not to familiar with the packages cruise ships offer, but I do know that you can have the wedding while in one of your ports of call. For example, there are several wedding planners in Jamaica that can plan a simple wedding on the beach (or your choice of location) for not too much money while you are in port. They will arrange for transportation and all ceremony/reception details.
I would suggest sending out wedding invites, you may have friends or family that want to come. On your invite, put your TA's info. That basically lets them know they will have to make their own arrangements. You can still have an AHR when you come back, but at least you gave people the opportunity to come.
Hope this helps a little! Good Luck