The city of Coeur D’Alene in Idaho has a great reference guide to trees suitable for urban settings. I’m not sure if all these trees would be approved by Toronto’s Urban Forestry Service (though it would be nice if they offered a similar guide for Toronto).

One of the ‘front runner’ candidates we are looking at planting (as suggested by my Mom) is a Crimean Linden tree. They apparently grow very quickly (great for carbon sequestration), grow to a size of 60′ high and 30′ wide, and (are rumoured to) naturally repel mosquitoes. Sounds like a great backyard tree, to me!