Dalhousie Community Center, while not a park, is often very quiet on the weekends and is a great spot to get back into it. The parking lot is relatively smooth, and theres some space behind the Jr High there to bike too. Good for a quick catch up if ya dont find a proper park spot to practice.
Practice in a parking lot for the first couple days, and then as you get braver, there's lots of great areas in Calgary, I mean it's kind of the mecca of cycling.. I don't know what kind of biking you are looking for, but nothing beats a Glenmore Reservoir lap. Big hill down and up weaselhead side, but just walk them if you arent feeling it, there's lots of signage warning you. Bigger ride, the loop is about 15km.
Downtown along the pathway is a good flat rip. Go at non weekend non-busy times, park at Pierces Estate Park and rip down to the peace bridge and back, it's fairly flat and a cool ride. It's not a ton of kilometers, and they'll melt away on this ride anyways, it's not that physically challenging.
Nose hill is always a classic too, but you have to be willing to do some hills. It's hard to find a good ride in the NW that won't have you climbing at some point, but I'm sure something is out there, we'll just need someone else to point it out for us.