there are full face snowmobile helmets that have a paper filter over your mouth , you could look into those online to see if it would trap dust/ pollen.
They are called modular helmets,
My snowmobile helmet ( HJC ) brand has fabric under the chin across helmet, that would block some dust as well

 

First rule to explain to a newbie, don't tailgate or you will be eating / breathing dust all day, If you all keep a good distance from one another and meet up at junction points , it will reduce dust by alot.
Its also not good for your air filter or clutch intake vent to ride in someone's dust all afternoon.
I'm not saying your doing that , just mentioning it.
My wife's air filter was always full of dust till i showed her how dirty it gets in just a couple hundred miles.

 

a member on here sells these with good reviews

https://wolfsnout.net/dust-mask-goggles-accessories-for-off-road-riding/

 

Thanks folks, great information and suggestions. The machines are at our summer home and we won't be on them again until May, but we'll have goggles and dust masks before that. I'll find us helmets that work (fit) with goggles & mask over the winter.
Also appreciate the comment on following to closely. Watched a friend get rear ended by his son on one of our rides which made me start looking at bumpers for our machines!
Learning........

 

I tried the wolfsnout and it just didn't fit my face with my beard.

I use one of these in the link below and it works great. Plus, you buy one and get 4 free so $20 gets you 5 masks.
https://safishing.com/shop/buy-1-get-4-faceshields-fb5/?gclid=CjwKCAiArrrQBRBbEiwAH_6sNKfPTuJu_cfDWEzVVVj8LNSbDBIPO5lSPgQ-LOaMQeVktneVr8ct2hoCsBEQAvD_BwE#configuration

 

30 second rule

X2 on the NOT tailgating. You will eat dust all day long and be blowing it out of your nose for several days.

We have the "30 second rule" that we go by. If you are stopped, let the first person start, then the next follows AFTER waiting 30 seconds, and so on. The dust is settled by that time and it works very well. If you are going faster than the person in front you and start seeing dust, slow down and wait for a few seconds.

Next thing is communication. We have Baofeng radios and run on the MURS channels. We both have in helmet mics and speakers with remote push to talk buttons on the left handlebar grip. This is perfect for communication, and no one feels like they will be left behind or get lost.

Probably MOST important is that the lead person waits at a Y or cross road / trail, and makes sure the person BEHIND him sees the direction he goes. Then those following, do the same thing. The motto is "every person is responsible for the person BEHIND them. If you dont see the person behind you for a while, stop and wait till you do. Then the one in front of you will do the same and so on until the whole group is stopped.

 

When we ride, mud or dry (dusty), my guys put navigation on me so I don't deal with the dust all that much. Unless of course we come up on another pack of riders. At which point I give them some distance until it's safe to get right up on them and hammer the throttle a few times making the Big Guns bark and they quickly move over.
My riding buddies and I do not follow the "don't follow too closely" rule as it's always a talking point back at the lodge as to who is the slowest of the group is and well we are competitive individuals so it's always fun.
I know a few of them do wear the Wolf Snout, others just blow filth from their nose for a day or so.
So I'd either have her ride up front or go with a Wolf Snout style filtering system.

 

When we “get bored” and ride local atv parks dust is bad since they’re so rode out its fine silica sand almost, so if it hasnt rained within hours its horrible.

Few years ago i gave our sponsor Wolfsnout a try and ordered the complete google, dust mask, tear offs. My schnozz has been busted twice so nothing fit proper, but i was extremely happy with this setup and it worked as advertised. Was able to ride just as hard as the leader or first couple guys since i didnt have to wait for dust to clear for breathing or sight purposes. Very affordable too, so if it dont work out, you can shit can the whole setup and not feel guilty about it.