DAS provides an accommodation for guests who have difficulty waiting in the standard queue. It is not based on a diagnosis, so be prepared to explain why your son cannot handle the standby queue.
The DAS holder must ride in order for the rest of the guests in the group to access that attraction, BTW.
Genie+ works well if you don't think he'll want to ride all the attractions the rest of you want to go on, or if you think he might change his mind a lot about riding at the last minute.