I did a split stay January 2010 between AKL and CR. This August I am splitting my stay between CSR and POFQ to get a taste of the moderate resorts.
I had no problem last time switching resorts. We just took our bags down to bell services at our first hotel before we left for the parks. They have you fill out paper work and give you a claim tag. We took a afternoon break from MK, headed over to our second resort, checked in, called bell services from the room, and they brought up our luggage. The only thing it cost us was some extra tips.
I have heard others say they preferred using a taxi to move between resorts to make sure there are no luggage problems.
As far as the tickets and dining plan with a split stay, here is what I am doing. The first part of my trip at CSR is 4 nights followed by POFQ for 3 nights. I have 2 reservations: (1) CSR, 8 day ticket package, dining plan for the 4 nights at this resort; (2) POFQ, room only reservation for 3 nights, no dining plan.
I have my best ADRs for the first part of my trip and then go a little cheaper that last half and pay out of pocket. Keep in mind that the dining plan starts on the day you check-in and expires at midnight on the day you check-out of the resort. While you only get the number of meals as the number of nights on the plan, you can spread them through the day you check-out if you are clever in your choices.
If you wanted to do the dining plan for the entire trip, then you need to turn the 2nd reservation into a package. You can do this by reducing the first ticket package by 1 day and then adding a 1 day ticket on to the second reservation. That way you still get some benefit of the multiple ticket discount.
Just remember dining plan must be part of a package but it is always based on the number of nights in your resort, regardless of how many days are on your tickets.
As other people have said, it is 2 reservations and therefore 2 deposits. In my case, I have to pay the $200 package deposit on the first reservation with the balance due 45 days before my trip. On the second reservation, the deposit was one night's stay with payment due on arrival since it is room-only.
Sorry if this is too long a post but I was confused the first time I tried to set this up. I had some really great help from these boards to understand the process. I wanted to pass it on.