Run around the Olympic Oval as many times as you can in a time period to see who can run the most laps or fastest 5K, 10K, Half Marathon or Full Marathon (Must be done in 4 hours).
It's always easier to train when you've got something in mind train for. Find an upcoming running event in your area and sign up, it's as easy as that. Train each week in preparation for the big day and then go out and have fun with it. You will have runners at all different levels of running abilities. You'll have semi pro runners right down to absolute beginners. Running is for everyone when you realise that the only person you're competing with is yourself - to gradually make those improvements and gains. Good luck on your journey.
Motivate yourself and your friends by downloading DOARUN - the worlds first interactive running game. Set up a running group and invite your friends to join.