We checked in at the hotel desk first. That way you get your park hoppers/room keys and can be on your way. The
DCL desk is open certain hours and you can go on any day that you're there--they check your info, license, etc. But the main desk is the one that has the KTTW card. They'll let you know the hours of the DCL desk--we did ours one morning before going to the parks.
HTH
Amy