I think volunteering would be good for them.
Or have a look at local age UK website for things near you, there will be guided walks, coffee mornings, men in sheds, walking football.
If they like walking, I'm sure their will be a walking group local to you. One near us meet via coach so go further out. Look at meet up it's just not for youngsters or just Google.
Join your local u3a group www.u3a.org.uk/ there will be lots off group activities out there.
If determined to not go out then knitting, crafting, puzzle books, jigsaws, model making, play video games, diamond painting, cross stitch, paper flowers, scratch art, paint my numbers, rock painting, colouring, board games. Take them to your local hobby craft I can never go there without coming out with something to add to my to do collection.
If they say no to all that, then tell them to shut up and stop moaning if there not going to try something.