Here are my initial entry ideas:
#13 is the full-color, touched up version. This would work for most things, such as websites, letterheads, etc. but obviously not for t-shirts.
#14 is more of what you could expect for silkscreening onto shirts for the participants. I added a distressed/textured effect over the top to give it a cool vintage feel. This would also embroider/stitch quite well, except without the distressed layer of course.
Let me know what you think, and we can work on revisions as needed.
Thanks!