It sounds like someone's coworkers need to get off their Puritanical high horse. This reminds me of one branch of the soon to be in-laws during Christmas "Dirty Santa" gift exchanges. They would always try to get the bottles of booze or wine, so they could make a statement by pouring them down the drain right away. Some people are just odd.
I'm with everyone else here, in that if your kids want to pitch in, spend quality time with you, learn about brewing (and fire safety if you're using propane), that's great. I personally wouldn't give them more than a sip or two of the finished product, but even then, you're not going to do any harm unless they're drinking in larger quantities. They're certainly not going to suffer any "harm" by helping brew.