Over Yom Tov, Ittisa & I took some of our children to one of the local playgrounds (not our usual). While there, there was one child (frum) who came in after we did, and started pushing around (not purposefully) other children (including mine) (such as climbing on top of them to get to the slide first, sliding down into other children, etc.). The parents of this child were shmoozing (and I did not know who the actual parents were) and did not notice what their child was doing.
What would you do in such a scenario?