My neighbor has a 6 year old child with pretty bad autism.  He hits and bites as well and is unable to communicate.  I think the best solution is for your kids (if they continue to be his friend) to tell him not to hit.  She is always telling him "No!" firmly.  So I am sure that if you tell him enough times, he may understand.  If not, your kids and you would have to make a decision on whether or not to have him as a friend.  I would at least let your kids try to be friends with him because he is unable to control his behavior problems. 

 

I’m not extremely familiar with autism, but I can tell just by watching my neighbor and her son, that it is extremely hard to deal with. 

 

Good luck and I hope that your children and you can figure out a solution for the problem.  I would try telling him no, and if he doesnt get it, then you would go from there.