Port Cunnington on Lake of Bays.
http://www.portcunnington.com/
"Port" was a special treat for my brother and I when we were staying at my Aunt's cottage. My grandparents knew the then owners very well. My mom tells stories how it took a full day to get to "Port" from Toronto by rail, then water taxi when she was a child. My grandmother bought a parcel of land in the '50s as a wedding present for my aunt and uncle that was very close to "Port".
As a kid, "Port" was rather rustic and very laid back. They allowed the cottagers to tie up at the dock and as long as some little thing (like an ice cream cone) was purchased at the tuck shop or staying for lunch or dinner, we were allowed to play all day on the beach and use one of the two water slides. At that time it was a family owned and run business.
Many times over the years our family would meet at "Port" for Thanksgiving dinner. The drive up could be spectacular with the leaves changing, or a bloody nightmare with rain, falling rocks and slippery leaves on the back roads.
The place was bought and is now being run as a modern efficient lodge, with very nice outbuildings. While it will probably suit your needs, it has lost the personal charm and the closeness it once held for our family.