Does he have a TA supporting him and play/lunch? Is it because it is both unstructured and busy?
Could he be allowed to go for lunch early by say 10 minutes with a group of 3 or 4 and a TA so that he hasnt got to que or wait in a busy hall. He would also then be out 10 mins early to run around before the rest aswell and back in 10 mins early for some down time/quiet time in the class before they come back.
At least he will still be out with others but also have a little free time to himself.
If the whole playtime is too much can his play be altered for a different time perhaps with a friend of his choice?
Is he perhaps overloaded due to not enough excercise so playtimes is a mad rush to get himself sensory regulated. Perhaps a couple of short breaks between more heavy thinking work as down time either excercise or quiet at a work station away from class so that its not a mad rush around and playtime.