I'm doing something similar in August--2 nights at WDW post-cruise, 1 day at MK. Even though Poly has been my dream deluxe, I decided CR made more sense this time around. Since it's such a short trip, the ability to walk to MK was the biggest selling point for me. I also booked TPV so we can watch the fireworks from the hotel room the night before we go to MK. I'm hoping this will satisfy our desire to see the fireworks so that on our MK day we can use that time to get in more rides. While I think I'd like the pool and "feel" of Poly better than CR, since we'll be swimming and going to the beach on the cruise and we're trying to maximize park time on the short trip, we probably won't take advantage of the pool anyway.