My daughter has high functioning Autism and we have had this issue before too. We didn't dose her with any melatonin or anything when she was that young... we did, however, talk to her routinely about coming to get Mommy or Daddy when she couldn't sleep anymore and made it part of her routine. As I'm sure you well know, the way to get kids with Autism to do what you expect them to do is make it part of their expected routine. Give him a sticker or prize every time he comes to get you or your husband and doesn't wake his brothers/sisters when he wakes up. Another thing to do is give him something he is allowed to do instead.
There are also alarms that you can get to let you know when he gets out of bed. They are called patient alarms and run anywhere from $200-$500. It's a pad that you attach to your child's bed that will alert you when he gets out of bed and you can get them, I think, from most DME (durable medical equipment) suppliers. These are not covered by most insurances and are typically used for the care of the elderly or cognitively challenged individuals, but are also used for people with sleepwalking disorders and so forth.
Do you have him involved in any Autism programs in public school? They can really help. My best friend has her four year old Autistic son in public school, even though her eventual goal is to homeschool, because they give him support and the routine that he craves. His behavior at home is better and he is actually sleeping better now. My daughter has also been in special education since she was 8 months old. You can really see the difference in her behavior and sleep patterns when she doesn't have the support that school gives her, even now at 13.
Also, go to DDD (the Department of Developmental Disabilities) and see what their advocacy groups can offer you. ARC is also a great resource and there are Autism support groups and advocacy groups everywhere. Getting involved with these groups is vital, I think, as a parent because it give you a place to seek advice from other Autism moms and many of them are very well educated in how and where to get help for things just like this. One suggestion made to me at one of these meetings was to see if you child has sensitivity to casein/gluten... a simple elimination diet can test for this. It's a change in lifestyle, but well worth it in the realm of sleep and behavior without medication.
I don't know what your financial situation is, but you may also qualify for medical assistance for all of your children. It is vital to your sons success if you can get him started with an occupational therapist at the very least. They can help you with strategies to meet his sensory needs and maybe help you find ways to help him sleep better or longer. I saw a piece of advice about changing his mattress/blanket... I've heard of this. Our OT suggested that we try having our daughter sleep on a magnet therapy mattress pad. They are very expensive so our OT's office offers one to try out to see if it will help before you buy one. It is not covered by any insurance as far as they know. Our daughter's diagnosing psychiatrist automatically referred her to the Childrens Sleep Center because kids with Autism generally do have sleep disorders. They can give you answers too.
I strongly recommend seeing if you qualify for medical assistance. It can help you make sure that you can get the care and therapies your son needs for his Autism. You can also go to Social Security to see if your son qualifies for disability... which includes automatic Medicaid benefits. It can be a huge hassle, but they will also help in getting him what he needs. It's hard to be an advocate for your child, but so worth it when you see the results that are possible with the support of different agencies and parents who, like you, are just doing the best they can for their kids with special needs.
Good luck.
