Vince-
Yes you can call and apply the code to your ressie and then buy your AP later. AT MCO (assuming you are flying in) there is a Disney Earport where you can buy your AP and they will activate it for you right then and there. That way you will have the activated pass in your hand, which is what you need at checkin. This eliminates you having to go to DTD or to a park to activate it before you check in. I have heard that sometimes if you show your voucher at checkin and tell them you are going to go activate it, they will let you slide, but I have also heard that they have made people go activate first and then come back and check in. Just some info you may need.