DS is 8 and recently we bumped into a boy (let's call him Harry) from the year above on the way home from school. We were walking home and he was scooting down to the park on his own. The park is about 1/2 mile from his house, there are sections with no pavement so he's occasionally on the road and the pavements swap sides so he needs to cross the road 5 times to get there. DS asked if he could go to the playground on his own with Harry. I'm not happy yet for him to be going on his own so I said that I would go too (embarrassing Mum 
). They played really well together and Harry seems like a sweet boy.
Today Harry knocked on our door and he was on his own again and asked if DS could go to play at the playground. Again I said that he couldn't go on his own but that I would go too. They played well together again although they did go through the bushes and I found DS climbing inside a dilapidated brick shed that I didn't even realise was there and certainly wasn't safe. DS and Harry asked if Harry could come over to play and I said he could if I spoke to his Mum first. Unfortunately Harry doesn't know his Mum's phone number so I said I would speak to her at school and arrange something. We went our separate ways and I noticed at one point ine distance that Harry was cycling on the wrong side of the road as he was going home.
So, now I need to arrange for Harry to come and play which I'm happy to do. However.....I DO NOT want DS to receive an invitation to Harry's house. It appears that his Mum is probably far more relaxed than I am and DS is not especially street-wise. It worries me that they would be allowed out of their house to play without any supervision and who knows what they would get up to in the house. All other playdates have been to places where I know the parents well but I don't know Harry's Mum at all! I'm sure it's obvious that I'm a worrier and I'm imagining some people will see me as being over protective but...how do I handle this?!