I have two children with autism, my children where diagnosed at an early age. One of the signs is speech, eye contact, hand flapping. My children have come a long way and frankly unless I told you, you wouldn't know, early intervention is key. You are in a very tough position, any parents does not want to know that their child has something wrong with them. I would express my concerns to the parents, suggest that they see their doctor, they will need to see a psychologist and he/she will run a series of test and they will determine the diagnosis. Best wishes to you and your daycare family.