Assistant Trainer Compensation

Hello!
Interesting scenario here:
My former working student is now teaching on her own for others, and doing training rides for my clients. I took a break from any kind of serious teaching/training (I have a non-horse job too). During that time, my clients went their own directions and my working student took on a teaching job.
Over the last 6 months, a decent number of my former clients started contacting me, and this fall an opportunity opened up for them to all be in a boarding situation that allows outside trainers.
Now, we are 3 weeks into this new arrangement, and I’m already going to a horse show.

So here is my question:
We have a large percentage of green/young horses, I am not currently riding. My former WS did a lot of the green horse riding before, and does now. I am trying to figure out how to be fair to her and my clients when she comes to shows with me to help out and possibly do some training rides. When I asked her, she said “I trust you to be fair”. Before, she was 17 and was getting a decent amount of perks (rides, show rides, trailering, training ect)
As a group, we do not have grooms, everyone (& SOs/Parents) pitches in for set up/tear down, feedings, everyone takes care of their own stalls, grooming, tacking, ect. For multi ring shows, having my assistant handy has always been a life saver.
What is fair? I am currently under priced for my location/experience.