Meaning of 'Central Ontario': Henceforth, Central Ontario refers to Wikipedia`s definition and the reddened area of Wikipedia's map (abridged by me) below, which excludes Manitoulin Island.
Central Question: In Central Ontario, are there any national parks or wildlife areas that contain roads or trails on which vehicles can explore the park?
Context: Residents of Toronto, my elderly grandparents desire to behold nature by exploring an 'authentic' national park or wildlife reserve, one situated truly in the wild and not 1 hour outside Toronto, preferably with natural water bodies. Alas, their feeble health and physician's warnings prevent them from hiking, and limit them to walking only around 15 minutes at a time.
To enable them to perceive nature, my grandparents were thinking of renting an off-road vehicle (with all wheel drive), to drive into the inaccessible interiors of parks (instead of walking all the way), and to stop and walk briefly only to access the most beautiful sites (eg: a scenic water body very remote inside a park).