At my former center yes there was a mandatory naptime. No child is forced to sleep but they must be on their mat and lay quietly. If they fall asleep great. If not, then depending on the child we would give them books or puzzles etc.
State requires that should a child not be asleep within 30 mins they must be allowed to get up and walk around. We never allowed that since they would wake up their friends and all heck is broken loose.
State law also states that naptime is no longer than 3 hours. Our nap was from 1230-230 so only 2 hours. Every child was required to get up regardless of what time they went down. The only exception we made was when we had a field trip and if we got back late then the kids would sleep until 3:00. However no longer than that.
Sometimes parents would say they didn't want their kids sleeping or they would ask us to wake them up earlier. Depending on the child we would do it or not. One little boy (3) was there at 6:30 a.m. but wouldn't get picked up until after 6 or later and the parents didnt want him to nap because he didnt sleep well at night. I refused. I said this child is here ALL day (mom was at school, dad at home, yeah I know!) and I wasnt going to make the day miserable for everyone just so he can go to bed at 7 for them. Well, I didn't say it like that but you know what I mean!
I think that if you just let the children all have a rest period and tell the kids that they dont have to sleep but they do need to rest, things will eventually work out IMO