We're up by you in the summer and we like to leave somewhere between mid October and the first part of November. Much later and you run the risk of snow and freezing temps. 
Remember that the deep south is still very hot for us northern types till about the end of November. It will also be the same at the end of March and April. IMO you will enjoy yourself much more if you take your time going south and then back north. Instead of racing to see all the snowbird destinations, enjoy the middle of the country prior to getting south, then settle in for the winter. Take multiple winters to see all the destinations.