You can charge about the same as you would for a pasta dinner in your town - what do those go for usually? Here I would say the $6-8 range is about right.
Krusteaz pancake mix offers a rebate I think - look on the back of the big packages.
Make sure your team is trained on how to be wait staff - nothing worse than being at a team pasta dinner/pancake breakfast, dying for coffee, juice, SOMETHING and seeing a bunch of students and mentors hanging around in groups talking...
Not only do they need to learn how to serve properly, they also need to be assigned tables and be attentive AND how to schmooze at the same time. "So... are you familiar with FIRST robotics???" as they pour coffee... and "Did you know that we built that robot (points) in a mere 6 weeks???"... and "I love being part of this team because....(fill in the blank)"... and "Did you know that our team relies on sponsors from the community because we are not funded by the school budget? Would you like to see our wish list???"... and "Because I'm a member of this team, I'm eligible to apply for $9M of scholarships to college!" and... well, you get the picture!