When band members are using the SQ mixpad app to set their own monitor levels (on their own devices), is there a way to stop them from accidentally changing other parameters? Many thanks in advance 
You can check the manual for sure but I believe you can apply user permissions to this purpose. However, what you are describing is really the reason that the 4You apps exist. Check out SQ4You app on your device App Store. This app is designed solely for allowing musicians to adjust their monitor mix and not other system parameters.
Oh awesome!! Thanks, I will check that out for sure!