Illinois labor laws, adding store hours
My employer (public library) has just decided to add one additional hour to the work week (open 4 hours on a Sunday instead of 3). Part-time staff (under 37 1/2 hrs, our "regular" week) get paid for that additional hour. Full-timers don't (tight budget, overtime not allowed) but must then take those hours off during the following week (not easy, as most of our "business"/programs take place during the week). The Board also wants us to have more programming during the week (now with fewer people/hours to run them).
Is there any recourse for people who were hired for a 3-hr. Sunday (who suddenly must arrange to work an additional Sunday hour)? Can we refuse without losing our jobs? (No input from staff re: adding hour.) Or be paid for that additional hour? We have <50 employees.