Dh thinks IABU and that we should let her go. I think that at just turned 10 she is too young to go alone.
...and before I get accused of doing AIBU by stealth, I will add that the group that have asked her to go aren't necessarily her friends - they are (in her words) the "cool" kids, and are much more streetwise than she is. They're a lively bunch (and at the risk of sounding judgemental, I wouldn't be surprised if at some point they were asked to leave) and dd is friends with one of the children because she is afraid of her
So, over to the mn jury - am I being unreasonable?