Creative Ideas Please! 12-14 yr old boys?

Hi I am a youth worker and provide relief 24 hour sleepover shifts with young people. Tomorrow I am going to work with two boys 12-14. They are very active and cause trouble if not kept busy, like doing things with their hands. They have x box and all that at the house but still get bored. I am looking for cheap or free stuff to do with them to keep busy and happy. I've got one idea to have a camp out and roast marshmallows (the house is on a big bush block) or maybe cook home made pizzas but im looking for other ideas from those who have experience looking after teenage boys or if you are one - what would you want to do to not get bored??