Niagara Falls is great. She might enjoy Kingston - a ride on the Wolfe Island Ferry is free.
A trip to the Toronto Zoo to see the pandas - we lived in Calgary during the Olympics and got to see the pandas. My son who was 2 at the time fell in love with them and from then on every time he saw a stuffed panda he wanted it - we have quite a collection in assorted sizes.
Grew up in St. Thomas and long weekend in August is Railway days with special events and long weekend in September is Fire Muster Days with a fire truck parade and activities.
If you look around the internet for some daytrips and festivals you might be surprised. Things like Black Creek Pioneer Village comes to mind.