My father and I will be traveling from Atlanta to Scotland with a 7 1/2 hour layover in Amsterdam in January. Would we have enough time to go into Amsterdam for a couple of hours or would trying to go through customs twice take too much time?
You won't go through customs again at Schipol before leaving, but you will have the usual security check. Not correct. Reentering Schipol for your flight to Scotland you will have to pass through immigration again as the UK is not a Schengen country. You do have time to head into Amsterdam for a quick visit. Store you carry-ons at the lockers inside the terminal....you'll see them shortly after you deboard the plane.
Regular customs checks only occur when you enter a country, never when you're leaving. I think what you mean is that checked baggage will automatically be transferred (if flying on the same ticket/airline) on to the connecting flight...no need to collect it and check it in again. If the connecting flight is via a discount airline, they don't transfer luggage, recollecting and checking into the flight will be necessary.