I would advise that you all get into Ski School for the first time so that you can nail the basics.
There are a number of good options in Mayrhofen, but from personal experience would recommend Ski School Habeler73 or SMT59. Both have offices in town and so you can pop into see them and ask any questions.
You can get some great online deals for Ski Hire with Rent for Fun25 at the bottom of the Penkenbahn.
Eating on the mountain can add to the holiday cost, however Pils Bar20 is probably the best value up on the Penken ski area.
Once you get here your reps will look after you and if you get into Ski School then they will help you with the skiing aspects.