As far as I know, they are open 365 days a year, so you should be able to make your ADR's that day. To be safe, give Disney Dining a call to verify that they will indeed be open that day. Also, try calling the day before that, as they may be able to do your ADR's then. That is what happened to me. Called to check on CP packages, asked if I could make my ADR's and we were off and running. Can't guarentee that will happen for you, but it does not hurt to ask.