There is a parking deck/garage that would charge you for like one hour. There is a pull up in the front if your party is there waiting for you, like where the Uber's pull up. There is metered street parking in the front and back of union station. Easiest by far is the parking garage.
If you're parking and walking into the station to meet your party, the parking deck is the way to go. There's a fee associated. If you're just picking them up, there's a standing line in front of the station comparable to pickup at an airport. Your party comes to you and you drive away for free.
Thanks! Your answer is awaiting moderation.