More and more popular, treetop circuits (also called canopy trails) are amazing outdoor playgrounds. With zip lines, wobbly bridges, ladders, tarzan ropes, they take "playing outside" to the next level. Just make sure they cater to your child's age before going to any of them.
Arbraska Treetop Trekking
Barrie ( 6 - 16 years old)
Treetop Walk with Eco Adventure Tours
Collingwood ( 6 - 16 years old)