Well, I'll give this question a shot. I'm pretty sure that if you purchase any voucher in advance, you won't be able to get the credit applied from the old ticket. Purchasing vouchers in advance is usually just strictly purchasing the voucher online or over the phone, and then getting it activated later. If you show up at a ticket window with a voucher and an old ticket, I don't believe they are allowed to give money back on tickets. With that being said, I'm pretty sure that the waterpark ticket windows are set up to sell any ticket which includes the waterparks, including the magic your way with plus pack option, and the premium annual pass. So if you were going to upgrade to either of these tickets from an old park hopper with plus features, they should be able to do it at the waterpark ticket window. If you were thinking of upgrading a regular old park hopper without plus features (which didn't include the waterparks), to a waterpark annual pass, I'm not sure they will do that for you, since it's a major park ticket to a waterpark pass. If that's the case, where you're trying to go from an old park hopper with or without waterparks to a waterpark annual pass, this might be a question for GoldenOldie, to see whether that's ever done or not. I know the water park annual pass would have to be more expensive than what's left on your original ticket, they can't give money back.