Hah, been there, done that
First question to ask of an unsuspecting Teacher / Jannie, is, "And how good are your smoke alarms ?"
After the initial panic

, they calm down a bit and let you explain that you're teaching historical fire skills......and it's fun, and yes, if the weather is good, it'd be better outside
The thing is that kids come in three varieties; those who learn by reading and then doing it for themselves, those who learn by watching & listening and then going for it, and those who only learn by doing.
The common denominator is that they will all want a go, even the hang back ones who say they don't.
Take more stuff than you think you'll need.
Take more kinds than just the flint and steel...........even lots of different tinders helps, and this is a great time for them to gather stuff......thistle down, fireweed, dried grass.....
I found that children love the firebow, they find the firespindle frustrating, they will hit the flint until it's a rounded pebble

They love handling stuff like the fomes and betullina, the barks, the cattail heads and the like.
Take something to smother flames too, just in case, and if you are using flint and steel explain that those little sparks 'will' burn clothing. A welders apron is a good thing to have, besides, no apron, don't spark, it gives some order to the 'my turn'.
Other things that I found appealed were rush lights, pine splints, pinecones that have been sprinkled with chemicals like saltpetre (burn with pretty colours), fomes glowing away and blowing it into flame. A blow poker and let them blow on a lit chunk of charcoal and watch it feed the flame........fire needs oxygen, kind of thing.
I also found it useful to explain that in Winter time there's really only eight or nine hours of daylight, that it's not only cold, but it's dark. No electric light, candles are waaaaay too expensive for most folks, so firelight and rushlight and crusie lamps were the best most had. Explain the relevance of fire; it's heat, it's light, it's the cooker, it's comfort, it companionship around it......
How long do you have to prepare ? and do you have fomes ? If you need some, let me know and I'll send you some as well as some that's been broken out and is ready.
I'm sure that if there's anything else, if you ask, folks will happily help out.
Best of all, enjoy it

The kids don't want a scared of them adult, you know your stuff, they know they're getting hands on something interesting, and at the end of the day your daughter will be chuffed to bits 'cos her Dad is cool
atb,
Toddy