Well, last year naeroscatu (Mihai) and I did Ward's Island one afternoon, and that was a great outing (ferry ride, quaint cottage community, skyline, docks, boats) but we never got to the old lighthouse. That's on my list to do again. And you can bring a bike, if you've got one.
Out my way, for airplane buffs, there's the Warplane Museum, and they're cool with tripods and such. The flowers will be blooming (if anyone shoots colour) at the RBG soon.
I'm sure there is lots to see up in the KW-Guelph-Milton area, even the Conservation areas, but I don't know what's there.