I'd endorse previous comments about St.Lawrence Market in Toronto (popular with locals and indoors) and also a couple of hours at Niagara on the Lake on the way home from Niagara Falls (30 mins away).
I'm a tour guide and go a couple of times every year.
Get down to the harbour and get a ferry across to one of the little islands (20 mins) and hire a couple of bikes or just have a walk. It's a brilliant view of the city skyline.
Best place to eat is Marche in Brookfield Place. It's a great concept, where you can go to various stalls to choose...