Hi my 15 year old DS has a school friend coming for a sleepover tomorrow. The plan is to meet in town in the afternoon, have some food, roam around then go to another friend's house not too far from ours which is by a park where they might play some football/hang our at the other boy's house. Not sure what is a reasonable time to ask them to be back bearing in mind I am responsible for the friend sleeping over? I said to be back by 10, DS says 11pm. Opinions please?