I would not recommend the Premier Passport, as it is full price for both APs at DLR & WDW. It is much more economical to get an AP for each park, especially with the
DVC discount at WDW.
Annie, you can usually find a three day park hopper at the local grocery store for a good price, which also comes with one Magic Mornings at
Disneyland (sort of like morning EMH, but for one park). This is useful for those not "staying on property". You can then have them add a day once there, I believe. I would suggest perusing the DLR board to see about the best way to get tickets at DLR.