SMS scenario to interact with customers - need help!

Here's what I'm trying to solve (maybe I've got a mid-week block going on):

We have people coming to our site that drive beautiful, classic, custom vehicles. Our social media guru has a series on FB/Twitter/Insta called #ParkingLotShots. We don't always know when the cars are in our lot.

What we want to do is to set up an SMS keyword that says "Text X to let us know what is in our parking lot.", capture the basic info from their text, maybe respond with an additional question or just a "Thanks, we'll come running" kind of message or even a surprise coupon discount to use at our counter while they are here as a thank you.