Is 200 miles in 40 days Healthy?

Me and my friend started a challenge to run/jog/walk 200 miles in 40 days. I am 5'8, 240 lbs(I don't even know lol, People freak out with my weight cause I look like Im only 210ish), 16. I am in decent shape and can jog 2-3 miles nonstop at a 8min per mile pace. My weight has never stopped me from playing anything and running alot :), but I had gotten a knee injury in football and just recovered(Literally). Main Goal: Have Fun, and show other overweight kids they can Run and need to stop being lazy. Sec : Lose weight XD. I LOVE RUNNING, but I am also concerned about my knee (Had a Meniscus strain/Tear). Other injures just came from: Ankle and Back (Not painful, but really discomfort when running)