I don't know if you are frequent on this board anymore, but I will leave it here in case you come back.

My son is 8, Dx with ASD at age 2, non-verbal until age ~5. I agree with above posters, you will need behavioral therapies. The school district will do evaluations and recommend services depending on how the evaluation comes through. The parents need to follow the ideas given by the therapists (esp. ABA) to get the most benefits.
That being said, IMO, just therapies are not enough. I noticed that extensive ABA leads to children being robotic. My son would even ask my permission to drink water. I didn't like it. He got so used to someone directing him that he would not do anything by himself. I stopped his ABA once he aged out of Early Intervention. The school district put him in a self-contained classroom with kids similar to his functioning level.

During this period, I did extensive research on Pubmed and noticed that there are known biochemical abnormalities in the kids with autism. If you address those biochemical abnormalities, you may get some mileage, depending on the child's issues. There is no yardstick for it and so it becomes really difficult to measure the benefit of any intervention.

Some scientists come into my mind. If you read their research, you will get some ideas. I will list some of them below.
- Derrick McFabe
- Martha Herbert
- Richard Frye
- Suzanne Goh
- Harumi Jyonouchi
- James Adams (Autism/Asperger's Research Program)
- Jill James
- Daniel Rossignol
etc.

There are actually many many more researchers but these are the researchers that are working on direct implementation than the theory (of autism) itself. You can take cues from their publications and dive in further to do research that may be relevant with your grandson. Many of them also have YouTube videos that you can check it out.

Then, there is Autism Research Institute Youtube channel. These talks are not very easy to understand as it is really hardcore research, but worth the time, if you can understand.

Finally, there is TACA (Talk About Curing Autism (TACA)). Look for your local chapter to talk to the fellow parents. Curing is a very strong work, IMO but from what I know, they are doing some good work. Mainstream medicine does not really 'approve' TACA's ideas, but the benefit one gets out of mainstream medicine isn't stellar either. So I do not get into those arguments but I look for what is useful for my son and talk to the physicians we are working with.

Hi- My son is 4 years old, non verbal, and on the low functioning end of the ASD spectrum. He was diagnosed at 18 months through our county's Early Intervention program, but you could also get an assessment through a developmental pediatrician. They recommend ABA therapy for those with ASD. He now goes to a special needs pre-school and gets ABA in the morning there and then pulled out for speech (3x a week), OT and PT (2x a week). Unfortunately my local school district (which decides his services) tries to save money as much as they can and denied me services outside of what he gets in school, so I am now trying to go through my private insurance to get additional ABA therapy in my home for him 2x a week. I am also trying to see if I can apply for medicaid based on his disability because another parent I know gets ST and OT for her daughter through medicaid. If you can also get parent training at home that would be very helpful (my local school district denied me this). I am paying out of pocket for music therapy 1x a week which he seems to enjoy. Good luck, I know I was confused going through all this at first and I am still learning new things every day.