Yep. We got home from Les Arcs last night and encountered that a few times over the week.
We had them in ski school in the morning, and they skied with us in the afternoon.
Our 9yo was mostly content to ski with us, and much of the time, I made sure I brought up the rear as he likes to play with going slightly off piste on flattish blues (where kids tend to go along the bank alongside), but that would slow him down, so I'd hang back with him.
DS1 (11) was the opposite and gone. We said to them both that it was fine to go a bit ahead, but that they must stop and wait for us at certain points. They actually got really good at doing that. Having them in bright orange helmets helps to keep an eye on them, too, and DS1 has a luminous yellow jacket, too. We'd tell them where we were going and ask them to wait at a point further ahead. Eg, when we skied into 1950, they'd wait near the entrance to it, or if we were aiming for a chairlift, they'd wait there.
We had to have a word with DS1 partway through the week when his attitude was pretty crappy because we wouldn't let him roam the mountain alone, doing reds and blacks. He was going down blacks in his lessons, so he was disgruntled that he was being forced to stick to mainly blues with us in the afternoon. We told him that whilst we know he's capable of skiing a black, he's 11 years old and will ski with his family in the afternoon, and his morning lessons are where he can push himself, under expert tuition. DH, whilst reading him the riot act, pointed out that he was damn lucky that we gave him that opportunity as we could stop lessons and keep him on blues all week if we chose.
I'm happy on reds, but I'm still slower than the DC. DH was a super nervous skier prior to our trip. Les Arcs built his confidence, no end, but he's still strictly a blue skier right now, which is why family skiing was based around blues.
We found runs that would allow the DC the chance to explore, slow down, and go off piste whilst staying near us to be a good compromise. For example us doing the Plan Vert blue, which runs alongside the Boardercross (small snow Park style run with bumps for jumps), or the Forêt run in Vallandry which takes you through Forêt Pitchouns but also allows runs off through the trees.
We would also say yes, they could do a red if it popped us all out in the same spot, but they had to wait there. Sometimes, I'd do the red with them, and DH would go round on the blue.
Lots and lots of talking to them about our expectations of them and the dangers of skiing alone. After the first day, when DS1 and I were separated after he tore off in a different direction and I couldn't catch him, we made sure he had his phone on him at all times, and we have Life360 installed. DS2 gets his in August ready for Y6, so we'll be glad to have that on him for our next trip, too.