Most tech volunteers have detail-type personalities with a fair measure of musician's ego mixed up, 'er, in. They have a genuine desire to do the job right. They have also invested quite a bit of time in making sure things go smoothly. Unfortunately, the only recognition most church sound engineers get is when things go wrong, like a problem with a mic not being on when it should be. Don't embarrass them.
Nothing hurts an organization more than a lack of communication.
Go out of your way to communicate any changes with this weekend's service to your sound team. Include them in on your planning sessions for all services and special events as early as possible. Your musicians and singers probably rehearse the material for the worship sets quite a bit. If you refuse to schedule soundchecks and rehearsals, then please don't find yourself complaining to your sound team about the poor job they are doing with the sound. Pray with them for solutions to the technical and relational problems they are facing right now.