I think as long as your confirmation shows the "click here for on-line check in" option then anyone can do it. My understanding is that it is more connected with a ressie than a person.
If you are not in their system already you will be asked to provide DL# along with CC info. You must be able to print out a receipt when you do this since you must show it,along with your DL & CC, to the clerk at the drive thru booth on your way out of the garage.