Yeh I would say this makes sense. I have always found ATL to be better for redemptions and UUA'S. It's an easy hop down to MCO with delta most likely and if booked far enough in advance should be fairly cheap. As the ATL will get in around 8pm most likely you may want to overnight at ATL. Plenty of airport hotels to choose from. This should make sure there is no doubt of a missed connection that evening ( assuming there is a late flight to MCO) but then its cut your holiday short by a morning. Its either a short taxi ride to an airport hotel ( taxi driver may not be the happiest, as I have found out) or the terminal connector to the domestic terminal and that dumps you very close to the hotel shuttle area.

With regards to the domestic connection problem. I have never had this issue but pretty sure I've heard stories that if you phone up and ask they "may" release a seat to allow the domestic connection. Hope this helps.