This is a difficult one, especially when we still don't know all the details.
It can seem a bit fussy to have lots of rules. But, it you don't have lots of rules, accidents happen.
The mountains are dangerous. People get lost. People have accidents. People get killed. Visibility can change. Weather can change.
You ski in packs or pairs. If you're in a pair, you only have to watch each other. If you're in a pack, the strongest skiers go at the front, and the back. Nobody skies ahead of the front skier, and the back skier doesn't ski ahead of the next last person. If the person at the front comes to a bend or a fork, or a difficult bit of terrain, he stops while the pack close up. If anyone falls over, the back skier will be there for them, and the front skier will still be leading the pack. The front skier will be experienced enough to constantly check that the pack is still in touch. But ...
If you are skiing at the front, and someone behind you falls over, and you are out of sight before you realise, then you were not experienced enough to ski at the front. And ...
Although I don't have children, when we have been on group trips we have spent plenty of time staring the children in the eyes and telling them you never ... ever ... ever ... EVER! ... ski on alone. If you lose sight of the pack, you stop. THE END! Do not try to find us. Stay where you are, and we will will find you. If you move, we can't find you. Do not move. You are only allowed to go skiing if you totally understand what we are telling you.
And, on our trips, no one ever goes skiing without a charged up Walkie Talkie.
Taking children skiing is not like taking them to the beach. People die in the mountains. However "over the top" you may think your precautions are ... they are not!
Obviously there is a lot more to come out here. But, as soon as you take a child into a mountain, you are putting their life in potential danger. How much you reduce that danger is completely down to you. And if you think that a particular child, or person, is experienced enough to take a particular role in the group - ski at the front, ski at the back, etc - if that person has an accident, then you may have made a poor judgment call.
If you are on a marked piste, every hundred metres or so there will be a post on the side of the piste. The posts on the left are marked in a different way from the posts on the right. When you come to a post, even if the visibility is down to zero, you can tell which way is sloping downwards, and which is up, and if you are on the left or the right. So you know which side of the marker is piste, and which is off piste, even if you can't see because of the weather. Of any member of your group is not confident with things like that then, frankly, you are "hoping for the best". Tragically, up in the mountins, "the best" doesn't always happen.