Try small non-load bearing carabieners both ends of the tape. That way, all they have to do is clip it into place.
Having young children on these trips is going to give any responsable adult grey hairs at the best of times. I suggest you establish a "sudden death" line for the kids. As in "don't go beyond that point or you might die suddenly and horribly." Just to keep it interesting........

By way of a small tale to illustrate the point - I went to see a friend of mine last winter over in Maidenhead. In order to get to her flat, I have to cross a local park. I had a bag on my back with a few EDC items in it. The park ain't lit, so I used my headtorch. Crossed the park, walked through an allyway and into her road. Took the head torch off and clipped it to my bag. My friend has a young son called Scott. Age 5. Nosey little sod. Asks a lot of questions. Every second one is "Why?"
It takes him a whole 0.01 seconds to spot my head torch.
Bear in mind that parks at night are dangerious places for adults let alone kids.
The subsequent conversation went some thing like this:
Scott: "Whats that?"
Me: "A head torch. I wear it on my head so that I can see in the dark"
Scott: "Why?"
Me " Because I have to cross the park and there are Monsters in the park."
Scott "Monsters?"
Me: "Yes"
Scott "Why?"
Me: " So that the monsters can see me coming."
( At this point, his mum is making your digging yourself in deeper... gestures behind him.)
Scott: "Why?"
Me: " So that the monsters can get out of my way."
Scott: "Why?"
Me: "Because I will happen to them if they don't!"
Scott: "Oh...."

The point I was making to young Scott is that the park is a no go zone.