I lived in Calgary for three years ( just moved to YHZ in 2008)

I took AC 146 many times ( AC 146 is the one your scheduled on for 0025 departure from Calgary) I would fly YYC-YYZ-YYT to visit my family in Newfoundland.

The airport is very quiet around this time, it's dead and all you see are the cleaners going around doing there floor waxing and what not. You have plenty of time to leave the airport, jump in a cab and go down Barlow Trail ( It's the road that takes you right onto the airport) There you will find Moxies Bar and Grill, Chili's Texas Streak House, Cactus Club, etc,etc. It's close enough to the airport it will only take 10 minutes in a taxi, Fare split three ways with your buddies won't cost much at all.
By the time you come back security will be a breeze because the airport is so quiet that late at night.
There isn't much to do at the airport as things start closing early. There is a 24 hour macs store on the departures level, outside of security, for snacks, drinks, smokes,etc. Delta hotel is also attached if you want a pricey supper there.

That's about all I can think of.