Keep this in mind even if your kids are under 8, for when they are eight and older. A huge opportunity.
When I was a youngster (!) from grade five through grade 12, I was a member of the Macoun Field Club, a kids' natural history club sponsored by the Ottawa Field-Naturalists and the (now) Museum of Nature. Until high school we met on Saturday mornings at the Museum and studied a range of biological topics, led by museum scientists and university biologists, and other field-naturalists, birders, herpetologist, botanists, ethologists.... We would meet at the museum or go on field trips for the half day (sometimes a full day if the trip was substantial). In high school we met on Friday evenings at the Museum. I am not certain about the current status of Fridays (the senior group may only meet for field trips?
The club had a profound effect on those who attended, in terms of love of nature and science. Many former members went into science and biology careers (parks administrators, Museum staff, university science departments).
There are no fees for the club and it is a "word of mouth" club, no recruitment; it is run by volunteers, and currently is housed in the building of the Fletcher Wildlife Garden at the Experimental Farm.
If you have children who might be interested (membership size is limited, and sometimes there are waiting lists, but typically there is space for those who want to join), I highly recommend this opportunity. It has changed many lives -- it certainly did mine. When you spend your high school years looking at bird feathers, you end up differently. In a good way.
In the 1980s I led the three groups of the Macoun club for a couple of years as we waited for a core group of volunteers to form a committee to help keep the club going, so I had the experience of being a member and being a club leader too. The club was named after John Macoun, a famous (to some) Canadian botanist. When I was in it as a kid, it was run by Ernie Brodo (retired lichenologist at the Museum of Nature); the 70th anniversary of the club is in 2018.
If interested: have a look: http://www.magma.ca/~rel/mfc/index.html