Your daycare, your rules, and you should stress that you want ALL of the children to follow the same schedule for meals, activities, sleep and everything else. You can say it nicely. If they have to change their schedule at home, then that's what they must do. THAT is NOT your PROBLEM!!!
I serve breakfast/morning snack as soon as all of the children arrive, currently that's at 8:30am. Then we are out of the house at 9am until 11-11:30 when we arrive back home for me to make lunch for 11:30-12:00. Then I serve afternoon snack at about 3-3:30 after nap. This way I'm feeding the children every 3 hours or so. It works perfectly for me, so the childrren who arrive at 7:40 & 8:00 have usually had an early snack with their parents at home to tide them over until 8:30 because my dcparents know my routine, period.