No matter how detailed your plan, something unexpected will likely arise. So it's a good idea to have a contingency plan in place. Throughout the term, determine points where you could intervene to change the direction of the program if something is going awry. Do you have a way of reaching out to all instructors to ask them to change their assignment direction if something ends up harming Wikipedia? How can you reach all students in the program if you see something that everyone is doing wrong? How can you make suggestions to Ambassadors to shift advice they're giving? Determining these steps ahead of time may save you grief when you're dealing with challenges when they come up.
Think about what would be so drastic that it would cause you to cancel the program entirely. And figure out what you'd need to do if you were to stop the program.