Calgary is relatively new city by international standard and "History" would not be a main attraction, although visiting Heritage park and spending a half a day there would be highly recommended for families with kids.
Summer time would be preferred due to weather and first 10 days of July is a must due to highly popular "Calgary Stampede". Book in advance. Winter is also great with very easy access to skiing and other winter activities.
Calgary, from my perspective, was a typical contractor city. It is filled with third world Asian laborers and educated Canadian management.
I did not like the culture at all. The Canadians all looked and dressed the same (like they are keeping up with the Jones's). The dinning is pretty good as there is a lot more import ingredients and workers. There Asian markets are impressive with selections of imported goods. The train will get you all over the place, the casinos are clean an updated, the malls are always full but never crazy busy. Aside from skying there isn't much to do but if you drive an hour in any direction you can find some great activities. Banff is the place to go to have some adventure.
Nestled up to the Canadian Rockies with a clear beautiful river running through it, Calgary offers about as much as a person would want.
The zoo, downtown and Stampede are all tried and true attractions. The city has a wide array of great and affordable ethnic restaurants.
There are many nice restaurants and many people live in the city. They have history and fairy nice place to stay.