Lots of people have been talking about food in Calgary. If you are looking for a nice scenic drive I would recommend High River for Fast Food/Soup.
The Hichin Post is a great little burger stand (A LOT better than Peter's), they use REAL stawberries in their stawberry milkshake and the burgers are made fresh by "Wimpy" the owner every day. If you are headed out on a Saturday go early as they get so busy they often run out of food.
For great soup sandwiches and homemade ice cream try "Memory Lane" It has a cute 50's diner feel and the ice cream is made fresh on site. Make sure to try the beef stew and the High River specialty "Medicine Tree" ice cream.
I wouldn't advise doing supper in High River though.