hi grandmother b,welcome to the group,its great to have you here as you give us a different take on autism.
i know your grandson playing computer games in his room all day might seem isolating, but to him its his inner world,his safety net and his routine- when i was younger i used to spend all of my time in my bedroom using the computer,my whole life revolved around it.
however,my support staff began offering me a regular schedule of activities every week such as going to longford park or walton park to see the animals, or special college to do the ASDAN towards independance course or animal therapy at david lewis college, and clubs for people with intellectual disabilities,they all involve my strengths and interests so i was very motivated to go.
for your grandson,im wondering would he be motivated to go and do a voluntary job;building or fixing computers in a computer shop,this would involve his strengths and make his self confidence better plus he might make some friends with the techies in the shop.
is he interested in photography? he could save for a half decent SLR camera [my dad bought one some years ago for around 400-500 pound, theyre called bridge cameras and are halfway between a full on SLR and a regular camera-so all the quality of an SLR without the complexity of options] and go photographing in scenic areas which would get him out in the fresh air,he could advertise his work online and who knows-maybe become a selling photographer through it?
as for art, he could sell his work online which might motivate him enough to join a local art group or program for people with autism,i know of a good site for autistic artists and theres a huge list of programs available but there may be none in your area-
http://the-art-of-autism.com/sponsors/directory-of-programsstudios/
i also know of a program in manchester,UK who may know of a local program if your in the UK but not in manchester you could give them a call;its called venture arts and has a load of autistic members they offer all forms of art there and your work gets put in a professional gallery.
i would go but its quite expensive.