The inability to forecast smoke and AQI levels adds a new and annoying kink to leading rides.
1) Prepare an email with the registered riders email addresses the evening before the ride, save it as a draft. You can also tell people the day before the ride that you aren't riding, but if others want to go on the ride as a leaderless event that's fine too. Your choice.
2) A couple hours before the ride, check Purple Air (I use the EPA 2.5 data layer, with the LRAPA conversion) or whatever AQI source you're comfortable with.
3) If the AQI is above your threshold email registrants that the ride is cancelled.
4) If the ride is cancelled, inform Brian. He'll turn the ride registration off, and put the word "Cancelled" in front of the ride title on the post. He'll also add any other info you'd like, for example, the ride will be rescheduled when smoke allows.
Wish I could think of a positive quip, but I can't.