I need your help!

I need to know how to pull the rest of this surprise off.

Back story. My girlfriend (41) helped raise her niece for a couple of years while she was still in town. There's about 20 years difference in age. She loves her dearly. We just visited her and her fiancé in Colorado in July. Both had a very hard time leaving each other when we were going to explore more Colorado.

I am able to fly them in to a nearby airport which is about an hour and 15 minutes away a couple weeks before Christmas as my girlfriend's Christmas present.

They will be here November 29. I need to know how to surprise my girlfriend with this...

I could go pick them up from the airport and bring them back to my house which they will more than likely be staying at I have my girlfriend show up right after we get home as she doesn't live here yet.

I could do a scavenger hunt that leads to the airport with them waiting as a final clue/treat/whatever you want to call it.

I could pretend I'm picking up someone from the airport for my parents and have her go with me because it is a long track so to speak to get there.

Or any other kind of ideas I'm not sure what I want to do yet

Ideas? Suggestions?