Try Wyndham-Carseland.
Very nicely treed. Sites are nicely seperated. Has a few playgrounds for the kids. There is a nice ice cream store nearby if that interests you.
Lots of different birds in that area which make it interesting (storks for example)
Not a far drive out of the city which is a bonus. (only about 30minutes outside the city limits - East on hwy 22x)
Swimming is available I suppose, but it is the bow river so it may be a bit daunting for a young one. Fishing is certainly an option though.
http://www.cd.gov.ab.ca/enjoying_alb...ion.asp?id=178