I think you will be fine. For my clients (I'm a TA) I would time it out like this...land at 1p, arrive at resort by 3pm, checkin by 3:30pm, half hour in room, leave for MK at 4pm, 4:15pm bus picks up, arrive at MK at 4:45pm. You will have 10 minutes to make your reservation. It's a little close, but it can be done, but only if flights are on time and nothing else goes wrong. That being said, perhaps making the reservation a little later (if possible) might work a little better. The kids are gonna be so excited when they get there, that they might not get as much out of the experience as they would a little later that day or perhaps another day. Hope this helps.