Depends on what kind of park people you are. For our family, we prefer a break in the afternoon to go back to the resort for swimming and relaxing, and then back to the parks in the evening. Or conversely, we like to leave the parks and go have a relaxing meal, and then return. If you are not wanting to lose time at the parks, then choose a non-park day. But if you are going to be at MK, personally, we would do it that day.