I dont know how many park days you are planning but how about if you go to
MNSSHP and cut one of your Disney days out.....then you would have enough for both! You can get into the party at 4pm so honestly it is like having a whole day in the MK! We have gone several times and even if you take time for trick or treating and the dance parties and the parade, you still have plenty of time for rides. The thing that takes the longest at the parties is waiting to see some of the unusual characters. Plus, as someone mentioned August is HOT and HUMID so my advice is to get up super early to rope drop parks and then spend the afternoon and early evening poolside before returning to the parks! We are annual passholders but when we werent I made do without park hopping and it worked out just fine!