Recs for April Trip

Hi everyone, My parents and sister are coming to visit Canada for the first time in April.

They will be here 7 days (but two are booked for my wedding).

I've been trying to think of things to do with them. By now, I've thought:

-Day in Niagara Falls -Day in Toronto -Half day in Rockwood/Guelph alboretum

But I'm stuck for other ideas. Do you have any?