I think that's a great opportunity to share your family's knowledge & enjoyment of chickens with other children & adults, also a teachable moment about consideration when it comes to handling small delicate animals. I agree, wait until 2-3 weeks, they'll still be cute fuzzy cheepers but much more durable at that age.
Depending on how cold it is in your area you may/may not need a heat lamp for the time they're in your vehicle and in the classroom, but perhaps you should bring one just in case. Even a desk lamp would be enough for that time.
I would bring a wire cage where the chicks could move about, peck at feed, scratch & bathe in a dish of dirt while the children gather around quietly to watch. You could prepare a brief talk about chickens to give while the children observe the chicks, and let them ask questions afterwards.
Certainly the children will all want to hold the chicks, and that will be a great time to teach them about treating small living animals with consideration. I teach my kids that "kindness to animals means treating them in ways that make them happy, not just you". The temptation is there to squeeze them tight because they're so doggone cute, and to hold them longer than they wish to be held. And that's often when animals bite or scratch to make their wishes known.
Who knows, you may start a trend for backyard chicken keeping with the families of your children's classmates!