Hey Melissa,
We also use Aeromic in combination with Shure Bodypacks. Our main Studio also holds up to 10 classes per day so we can appreciate what you are up against. Aeromic has traditionally been the most robust, sweat resilent mic with good quality of sound.
Best tips...
1. Have spare headsets available for instructors should they 'sweat out', keep them in a dry environment to air out.
2. Use a product like eGloop (corrosion protector) on the connector to the bodypack.
3. Train your instructors on correct use - and remind them again & again :)
Hope that helps.
Chris (Les Mills Auckland)
Chris Richardson "aka" Duckie
Group Fitness Manager
Les Mills World of Fitness
Auckland
New Zealand