In Whitchurch-Stouffville the York Regional Forest tracts run dirt paths through mixed hardwood, wide enough that walkers, bikes, and horses share them. York Region keeps the tracts free every day of the year for walking, biking, riding, and snowshoeing, and dogs stay leashed except at Bendor and Graves and at Davis Drive.
Next to those tracts, Bruce's Mill Conservation Park has hiking trails, a disc-golf course, Treetop Trekking, and the Sugarbush Maple Syrup Festival in spring. It is day use, with no overnight camping. You can fill a Whitchurch-Stouffville day on the mill property and the forest tracts, and you still need a pad outside town.
Whitchurch-Stouffville has no public campground of its own. Book the night at Sibbald Point Provincial Park on Lake Simcoe, a Newmarket trip, with Newmarket the nearest full town. If the van is short on sleeping space, look at RVs for rent in Whitchurch-Stouffville.
Musselman's Lake
From Coultice Park you see Musselman's Lake, the lake inside Whitchurch-Stouffville. The Town of Whitchurch-Stouffville put a spray pad and a shaded picnic area on the shore.
Cedar Beach Resort on the same water is seasonal leases and park-model trailers, not nightly camping. That is why Musselman's Lake has no bookable van night.
South of the lake, Markham is the next town and the Rouge is the next park day. When you want Algonquin, that overnight is a Toronto trip.