Next spring we plan to do the DDP and as a result have to buy one day park tickets for everyone in our family. My husband and oldest DD both have leftover park tickets so they won't need their one day tickets. Can I use both of their one-day tickets toward upgrading my youngest DD to a park hopper, or can I only use her 1-day ticket to upgrade her? Basically I'm trying to get her park hopper to cost me as little as possible, but wasn't sure what Disney policy allows.