I think if kids are without their parents, they should be old enough not to stare. If with their parents, the parents should be apologising.
I had the most horrificly embarrassing experience a few weeks ago. Ds1 like to copy noises that stand out, because it is part of his SALT that he copies noises and mouth movements for a few minutes every day, and we reward him for trying hard with this.
We were in a cafe, and a woman who I see around (small town) quite often came in with her daughter, who uses a wheelchair, and is quite disabled. She doesn't speak, but she does make a lot of loud noises.
Ds1 didn't even see them come in, but as soon as she (the daughter) started making noises, he started copying, loudly and clearly. I tried so hard to explain to him that now was not a good time, but in his world it isn't strange for people to start making noises at him and for him to copy. I really didn't want to put him off copying, it has taken so long to get him to do it in the first place! We couldn't leave, I had ordered food. I wanted the ground to swallow me.