Your two boys are both at a good age to enjoy a trip to the zoo so i would say thats a great idea for a day out. Also yourself and your wife can enjoy a trip down memory lane and see what changes have taken place as i am sure there have been plenty of changes in
Toronto in the past 10 years.
For more ideas of days out you should check out the
Things to do in Toronto section of the website. This will give you information on Museums, Tours, Attractions etc. I think the kids would enjoy a trip to
Ontario Place where there are amusement park rides, movies and shows. I hope this helps.