I would send out a letter ASAP noting the way the dates fall this year and noting which days you will be closed. As noted above typically you would pass the weekend Stat to the next business day. Since your contract is worded differently I would just clarify it now and make note to change your contract asap for new people coming in.
I would assume most of your families also have the Tuesday off as they would be shifting their stat day over as well. Inform them now so they don't plan a "me day" thinking you are open when they have the day off!