The rates you have are very good for the dates of stay you require. This is high-season in T.O. If I come accross something less expensive, I'll let you know.
If the family is interested in theatre you have Mamma Mia! (the smash hit musical based on the songs of Abba) and The Lion King (Tony award-winning best musical).
Also the Harbour Castle is right next to the ferries that cross over to Centre Island. A quiet park/picnic area that houses some protective residents (but only a select few of them). The ferry ride offers a nice view of the skyline of T.O. and is relaxing if you run out of wind during the day.
Also, if you have never experienced dining at a Movenpick restaurant(also close by) you should try it. A restaurant under the concept of an open market where you walk from station to station choosing your meal having it prepared before you. You have your meal passport stamped and pay on the way out after you have eaten (note: the only restaurants where tip is included in your bill). Very fun especially when there are many people in the party with different tastes.
I personally like the Harbour Castle, it;s a nice hotel with a nice lobby and the service is not all that bad. I mean they won't kill themselves serving you. But then again, most downtown hotels in major cities are like that. You'll be fine. Just smile.
Enjoy your stay in Toronto.
------------------
Got points ? Got smiles !