I lived in Amsterdam for a while, there is an awesome campsite called Zeeburg which is a ten minute tram ride from central station. You can camp in tents, trailers, and caravans. They have wagons and eco cabins you can hire too.

If you are going in summer, it's perfect. Really chilled out, has a shop for food, a cafe and bar, Wifi, and overlooks a fjord where you can can go canoeing in boats hired from the campsite. There is even a secret beach in Amsterdam, which you can get to by canoe. Remember to wrap pack your beach essentials in a watertight bag so you can roll one when you get there :)