Stay with his friends

Yesterday my son really wanted to go to his friends house and he kept bugging me to let him go visit him. So we went to his friends house and when we were there his parents were not home only the big sister so we went back home. Today he asked me again to take him to his friends house and we went there again as he was knocking on the door nobody was home to answer it so we went back home again. After a few hours his friend called and he said that they wanted to pick up my son to go to their house after a few minutes they came over and picked him up. My son never get to stay at a friends house unless they are very close to us but this boy needs my son because he lost his big sister last month and my son is the only friend he has.