I have been up to the North Rim in September and it was cold at night. About that time the leaves were turning and the Aspen trees were beautiful.
Look up Locust Point as it is a great destination for the North Rim. It is mostly mountain bikers that frequent that location, but it is still small enough to feel like you are not in a tourist trap. Fire roads to get to it are easy, might have some mud and standing water from the melt though in some low places. You can literally camp right on the edge of the canyon.
Here is the view just 15 feet from my tent on my trip there to ride my mountain bike.
Full photo album linked below. You can hike the trails, but not ride them on the motorcycle, just so you know.