There in lies part of your job with your friend. To keep the prices a little lower than the going rate to move em out quickly and efficiently thereby reducing the hard part for you.
They will sell themselves if in good condition, cleaned and running nice with good cases and some accessories. You probably will not have to do much in the way of salesmanship. Really good photos are key. You will have more fun than you think and will be rewarded with huge smiles when you see how happy the peeps are when they carry off their prize. And I must say when it is a preteen or teen that gets gifted a vintage machine whether it is a FW or full size it just melts your heart!