In reply to pookie:
Hi,
I take lots of kids on Via Ferrata, it can be great fun or very stress full depending on many factors.
For the lanyards its not really about fall factors, its about them being able to deploy the shock load system on the lanyard, young kids are to light so they don't trigger the system, so can put a dangerous amount of force on their bodies like falling and a standard sling, also slam's them in to the wall with more force.
When working its the standard practice to rope under 18's up, this is mainly to deal with the issues of clients messing the clips up, (it happens more than you think), it has a few advantages but one of the disadvantages is you are a distance in front of you kid if they get scared or need help.
The other options is to climb behind them where you can assist them and talk to them. The issue here is it's a judgment thing based on many things, and like any judgement you see lots of people get it wrong. Its not officially recommended as it leaves a more scope for things to go wrong compared to roping. it relies on the parent being able to manage it with no slip ups.
Every year I hear of issues on local routes, some stand out examples are.
1) Mum takes two daughters straight on harder route, the first daughter gets past the hard section the second couldn't make it, so mum and her down climb. leaving the fist on her own and out of communication. fortunately she was collected by another group and they helped her to the top.
2) Boy falls from a route after he struggled with his clips and dad tried to help, ended up being unclipped and fell, lucky to have no injuries.
3) Dad dies after falling while unclipped with his kids, believed to have unclipped to help his kids.
I am not trying to put you off, it can be great fun taking kids on via ferrata, I really enjoy it. I took my mates little girl on one yesterday. but its tricky to advise, as its a judgment call based on quite a few factors to take in to account. The best advice I have is to start on the shortest easiest route you can find and see how they and you find it then move on to harder and longer routes, as you feel is wise.