This happened to me before. Have them share the space each coming 2 or 3 days per week ( mine each came 2 days, I took the lighter load on Fridays) then fill your other spaces, tell them you will do your best to accommodate them ....... And then do your best and see what happens. I would never take a big loss in income to maybe have people return from mat leave..... People have really good intentions but in the end they always do what suits them at the time..... And a year is long way away....
Just my two cents...