In town Sunday. Stopped at a bench to put my backpack down and rearrange it after exiting shop. Had DS14 and DD10 with me.
A random bloke about 30 I would say - didn't take much notice - just stood near bench looking at phone.
I'm sorting my bag, DD is slightly behind me to my right side, very close to me. Said bloke is about 3m away also to the right.
DS is behind the bench so directly opposite me passing stuff to put in backpack.
Sort bag, move on.
When we are walking home, DD says to me she feels weird. I ask what about.
"You know when we at the bench, that guy was stood there.... Well he kept staring at me and he was smiling but not. Like he was half smiling, like a little bit and now I just feel a bit weird" 
I told her if she had said to me at the time I would have confronted him. She said he kept on so she shuffled round me to hide.
DS chimed in that he saw him and glared at him and he then looked away.
I was so angry at the time that she felt that way. She is 10 years old.
I don't really know what I want anyone to say, it's just playing on my mind. I'm so saddened this has happened and she is only 10. 
How do I prepare her for this type of thing? Do I brief her? It's gross. Things like this happen to me but now I am older I have an excellent "Fuck off and die" stare that works quite well and would have no qualms confronting a guy if I was pissed off enough.