Power of attorney

Hi, I’m helping a friend who has just had a stroke (thankfully she’s not affected too badly)  and we have talked about LPA for her. Her son is 24 and on the Autistic spectrum (dispraxic, communication etc). He doesn’t work but does understand money to some degree. 
if my friend wants to do her own power of attorney could her son be one of her LPA’s with someone else ? She is an only child and has a small elderly family. 

I’ve tried looking on other sites/research etc but can’t seem to find any guidance ? 

many thanks