Yes we know this friend well, GagaJo, in spite of having difficulties in his childhood, epilepsy being one. His mother came round to see us the first time he came away with us to tell us that and didn't like other children knowing about it, although my son did, but he trusted him not to bring it up with other friends. We always took friend aside every day whilst he was away with us to quietly remind him to take his medication. He was absolutely no trouble, always has been easy to be with, more so than my older son, his friend, who has an up and down temperament and at times has been challenging. My son is also close to friend's mother who was very kind to him when one of his relationships broke up.
I know from my own growing up years that friendships with friends' parents can be rewarding.