I like the idea of 2 different spots, one with school in service days, and the other without. The other way I can think of is offering those days to each of them on an alternating schedule. Parent A gets the first school closure day, parent b gets the next one. If they want to switch, they arrange it themselves. I've also let 2 families share a spot, and let them do all the figuring, and have their schedule and payment ready at the beginning of the month. That worked pretty well for me. They were lucky to be able to split daycare costs, so they should do the extra work associated with sharing a spot.