If the weather’s good there’s a fair amount to do. In the city you can go to the islands, which is good for a half day – you can rent quadricycles, amble around, see if you can find the “clothing optional” beach, rent canoes etc.
The Distillery district’s not bad, and St Lawrence market is interesting enough too; High Park has a mini zoo (world-famous escapist capybara) plus lots of green space.
Out of town, there are a heap of wineries on the way to Niagara, about an hour’s drive away – Henry of Pelham does a good lunch, Mike Weir does brunch, and so on.
If you can stretch to it, Langdon Hall is a lovely country house about an hour out of town (different direction), with a very nice spa and restaurant – they do cream teas as well which are tasty.
For biking, if you have your own bike the Don Valley has trails, mostly unmarked (that’s in the city, so rideable from wherever you are). Within an hour’s drive, check out Albion Hills, which has purpose built mtb trails plus wide tracks for the kids and family to ride on. Further afield, Hardwood Hills is worth a visit, but about 2 hours’ drive to get there.