Honestly, the risks for those are, in actuality, very low. Autism (I have a daughter with autism, worked in a school for children with Autism, and study autism), is caused by genetic and chromosomal factors, and more and more often, they are beginning to find the deletions and mutations that cause it. It doesn't really have to do with advanced parental age. For the other occurrences, like I said, rare to happen, so try not to worry.
My ex and I had no risk factors for a child with special needs. We were 20 and 25 when we conceived, and still ended up with a child with a neurometabolic disease and autism. Our other son is perfectly healthy. It can happen at any age, but rare to happen at any age, and from experience, having a child with special needs has been an uplifting and humbling experience for me, personally.
Try not to worry too much. Your chances of having a perfectly healthy baby are MUCH MUCH higher.