There is no reason for all three of you to go through at the same time. You should stand in line first, with several people between you and your wife and child (they stand and go through together). You take the fewest items with you. Lock your wallet and other valuables in a bag that goes through with your wife.

Frankly, I think all of you should opt out of any body scanning, for health reasons. Make sure you are finished with all screening before your wife and child start through. You can pick up their items coming off the x-ray belt while they are dealing with the pat-downs. Stand nearby in case of any problems.