ive walked away from a lesson(out of like 4-5 ever)with paper in my hand and nothing new in my head.They will enjoy learning a few licks,runs,riffs(based on skill level of obviously)at first much more than memorizing scales,modes and progressions.
Their desire to learn theory will grow when they want to understand how they are playing the things they are(You know what I mean!).
Even if its just a simple power chord riff or something they will leave knowing they CAN rock and will desire to learn more.
Its kind of like being a kung-fu teacher.The student will come back if the teacher shows him a few killer moves the first few lessons rather than punching the air 50 times.
Try once,fail twice...