I think it entirely depends on the kids. If they are good listeners, and will listen to parents / your instruction, then have at it. I let my girls hold my baby, we sat on the couch and I sat between them. But there are neighbor kids I wouldn't let even get near her cage, let alone touch her.
Back when I had my JCP (many, many moons ago) I used to take it to the mall and sit on a bench with him. Little kids would run up and I would let them pet him after instructing the direction to pet etc. I never let any of those kids hold him, but he would drape around my neck and the kids would pet his back end.
Another option is sitting on the couch with them, letting the back end drape across their lap and keeping her/his head in your lap.
Don't be afraid to stand up for your snake, if you get a bad feeling about the kiddos, politely tell the parents that you would rather them not hold him, and just let them pet. Or that you don't feel comfortable doing it at all.