Wow! The response to this is amazing! Thanks to everyone for their thoughts!
More detailed thoughts I've had...
I was thinking no younger than 12 and even then only with specific parental permission and assistance (I was going to make them do a safety form similar to what I used to do with my college students). Everyone already has to wear goggles and we're just doing boring simple things so far (I'm more paranoid than I may sound). For this I'd make them wear long sleeves/pants as well as a lab coat or apron (closed toe shoe, glasses only/no contacts and all the other standard lab safety stuff still applies). Gloves too. There is a place we can use with an eye wash and emergency shower. There are no fume hoods but it's a very open well ventilated area- I'll have to practice the lab there first before I make that final call though.
I have a couple scales and they go to the mg level (one does better but just one scale would cause students to rush and that's the last thing I want). So this would depend on the recipe working with mg level measurements.
I think I would actually premix the NaOH solution and I would control it. I'll do something else to show them exothermic reactions.
Essentially, this is meant to be a high school lab (but if parents wants I'll allow mature jr high students to do it too). If it doesn't work out or if the kids start acting like maniacs in the slightest during our other labs, I'll just drop this one from my potential lab list. If everything works out and we do the lab, the younger kids would have something else that month. I just really don't like just showing them and telling them about something. If I can't have them actually do the reaction, I'll just skip it.