Hey Maura!
Glad you're thinking of making the trek up to Canada!!
I think the main attractions, from a tourist point of view, are the CN Tower, Casa Loma, the Ontario Science Centre (more for kids), the Royal Ontario Musuem, the Toronto Zoo, and the Hockey Hall of Fame….not sure if you’re interested in any of those. The ROM is pretty cool now that they've redone it. You can get access to all of them with a CityPass from TO Tourism. I really like the cultural side of TO – the arts scene is pretty great…if you are into theatre, check out torontolivetheatre.com. The Distillery District is a cool place to go for dinner and to walk around, I love it down there. The TO islands are nothing special IMO.
You can also go on a day trip to Niagara Falls or Niagara-on-the-lake. When FI and I were last in NOTL, we did a cycling winery tour that was fabulous.
Hope this helps. Keep us updated on your mini-moon plans.
Kate