Hello from a Calgarian.
Will you be staying downtown? If you are, take a ride on the C-Train and travel Southbound (as opposed to Northbound). Get off at HERITAGE station. Heritage park is a 10 Minute walk WEST from Heritage station (up Heritage Drive). In front of the park you will see an S-2 (or 4) Switcher coupled to a Caboose and our dear Selkirk. I doubt the park will be open when you arrive, but looking at these 2 fine locos is well worth the walk.
There is a lot of CP action right downtown (along 9th Ave). It is the CP main line! You will see lots of unit trains with SD40-2s, AC4400s and SD90-43s. Even some GP-9us. On 9th ave and 1st southwest is the shed containing 2816...a hudson with some heavyweight passenger cars, and a few F units. This is the train they use for excursions. You should call CP headquarters and ask if you can get a tour of this beautiful train.
If you are able to rent a car, I would advise you to take a trip to BlackFoot Trail and Ogden Road....that is where you will find CPs main Alyth yard. Of interest is the locomotive 'upkeep' facilities and locomotive testing facitilies. I usually find 3 or 4 locomotives of interest down at this yard......Warning....do NOT go on the CP property, you will be quickly arrested....Farther South on Odgen road is Ogden Shops.
We have 2 'main' train stores in Calgary. The one you NEED to go to is called 'Trains and Such' They are located on 4th Street and 24th ave NW. Call a cab, he will take you there. The other train store is called Hobby West. It is located on Mcleod Tr S and 50th Ave SW. I personally do not enjoy this store....I would give it a 5 out of 10 and Trains and Such a 10/10. Much better people and Trains and Such is dedicated to trains.
If you can, you should travel west on the TransCanada between Calgary and Field. There you will see Canmore, Banff, Morant's curve (on 1a just after Banff......1a connects back on to the transcanada), Lake Louise, the sprial tunnels and finally Field. Worth the trip if the roads are nice. If you plan to do this, I would strongly advise that you leave in the morning around 7 or so, so you have daylight the whole way.
I hope this helps, and enjoy your trip. I will be out of town (im off to Japan for 5 weeks starting in Feb) so I wont be able to show you around. You should call Mike H and get a tour of his layout.
David