I think that your calling out that pot smokers should be respectful of others around them was absolutely the right call.
Better to have the issue out there and known vs. a surprise that might offend, upset, or hurt people with allergies to smoke.
That said, with all of the GGGs that I have been to, everyone who does partake in smoking has been great about asking if it was okay or if it would offend.
It has been done descretely and not in the open of the whole group.
If the past is any indication, those who enjoy smoking will congregate together and will do so away from the rest of the main gathering.
If anyone where to have an issue with the activity being too close them, I am sure that a polite and civil conversation that is not judgemental about the activity can be had and accomodations will be made.
As I have said in the past, some of the best people I have met are my fellow backpackers/BPLers....I would be shocked if there were problems over this issue.
If someone is not comfortable talking directly to someone who smoke, feel free to talk to Ken or myself and we can bring it up with the person.
We are all here to have fun.