I agree the G Scale smoke unit looked awesome and it was probably better suited outdoors or at least a minimum having several windows left open. A one person noted that, a single 6 sigma case shouldn't be used as the measure for a public display not to use smoke.
A sign could be hung simply stating that those with asthmatic conditions should be aware of vaporized mineral oil being used. It isn't really smoke as it isn't being burnt like a cigarette releasing noxious gases and carbon.
All my life I've been plagued by cigarette and cigar smoke as it simply bothers me when I walk into a room or even if someone is smoking one outdoors. I don't coke or anything, just bothered by it. However vaporized mineral oil, aka train smoke, doesn't in the least bother me. Everyone is a bit different and thus the challenge as to how to appease everyone.
In this case, the use of smoke is for display purposes to get the kids and adults interested. Many on this forum complain about not attracting enough "young blood" well here is your chance to do that by evoking their imaginations with the smoke units running. They can just see themselves doing the same thing at HOME with their own trains on their own pike! This goes for some Dads as well!
Make it fun and they will come! 
