absolutely...maybe instead of naptime they can offer your child a coloring book to color or maybe be a teacher helper when the other kids are resting..my son loves his chocolate milk and it actually calms him down a little....but each child is different. :-)
My daughter's kindergarten had "rest time" for 20 minutes in the afternoon last year. However they did not want the children to sleep and would wake them immediately if they fell asleep- the idea was just a little quiet down- time so they could make it through the day a little more peacefully. By the end of the year the teachers had pretty much given up on it and the kids were getting an extra 20 minutes of recess instead. It was the schools first year of full day kindergarten.
I would ask what their expectations are regarding resting- 5 is a little old to expect them to sleep, although some still will if given the chance. In daycare they have little cots and the lights are out and the teachers are being very quiet and playing soothing music, and they all have their blankets and stuffed animals from home (at least in the places I have worked), but at school they got a beach towel on the carpet and if the sun wasn't shining the teacher left a light on so she could work, and there were people coming in and out of the room pretty frequently. It would be reasonable to ask that he be given books or coloring pages or headphones if he hadn't fallen asleep after x amount of time.
Taking a nap in kindergarten is a thing of the 60's. Many schools stopped having kindergarteners take naps when pre-schools became popular. Kindergarten now-a-days is like the First Grade classes back in the 60's.