AFAIK, there's no way to lock down the mixer on the surface itself to limit access to specific functions. Someone that wanted to muck with settings certainly could.
The neat thing though, is you can save all of the settings, so once you get it set up the way you want, you can easily reset the board to that state after someone's had their hands on it.
The native app is the same way. It gives full control without the ability to add restrictions.
However, there's a third party app called Mixing Station that lets you customize what the app looks like and what controls you want to make available. It's pretty easy to work with and could let you build a simple profile for the inexperienced users.
