The easiest and most cost effective thing to do is to create a package with your first stay - room, tickets (with enough days for your entire stay at both resorts) and dining (if you want it). Then do a separate, room-only stay for your second resort and use your park tickets from your first resort. Adding dining to the second part of a split stay is not cost effective as you have to buy more park tickets in order to do it. Unless you think you can use the additional park tickets at a future date. If you are willing to forego the dining plan for your last three nights, it won't be that expensive.