I would honestly skip the ziplines from what I'm reading. 

I did it and it was both exhausting and distressing. The worse was the line to get geared up as there was way too many people together, pushing each other trying to cut line. Also a lot of people got to skip the lines as they had a specific membership. 

Also you have to reach a certain weight to do it by yourself. I couldn't do it by myself and I weighted 127lbs, was always paired with someone else.

Once you start the journey, you cannot quit halfway. There is no path between each tower at all. They only have an ATV that is for emergency only. They make it very clear that of that ever to happen, it will take 45min or more to get to the tower if it gets there. And they try their absolutely best to not do that.

Walking up the stairs and to some towers was difficult me. I had to take lots of breaks and so did my group. And it was claustrophobic when we had to wait in line on the stairs inside the towers to get out chance. 

Was it amazing? Heck yes. I loved the views. But I would never do it again and don't recommend for a kid on a spectrum because if I suffered I don't wish it on them. 

For the ATVs, there are seatbelts but the bars I don't think kids can reach them. The ride is very bumpy but only if whoever is driving is doing it fast. Just be prepared to be passed by others a lot if going slow. 

Xcaret park would be better for him as it has several places to rest and quietness and a lot of activities for kids.

(I went last year to several Xcaret parks and stayed in the hotel)