["My son was invited for a sleepover but we don't know the host family very well.", 'Did you decline? I would not feel very comfortable until i got to know the family.', "Yes, and it was hard to decide because my son really wanted to go.  But you can't just trust anybody these days."]
I agree, you made the right choice. And it gives you time to get to know the hosts before a future sleepover!
I was unsure about letting my son go to a sleepover since we didn't know the family very well.  It was hard to decide what to do.