We may use airmiles to redeem three day hopper Disneyland tickets, but really need four day tickets, so can we upgrade at the gate? How much will it cost?
We have with no problems... can't remember the cost, you should be able to find it on the Disney website or in the ThemePark section of the boards, there's a ticket sticky.
Just use your tickets to enter the gate of one of the parks then go to Guest Services with the used tickets. They can then upgrade them by adding days, hoppers etc...