It fits perfectly into what you are doing. Could be a great boost to publicity.
http://orienteering.org/world-orienteering-day-may...
Cool! I imagine OUSA as a whole will want to participate. Maybe we can get 100 school events in the USA on that day, May 11.
Given that May 11 is a Wednesday, it should probably be called "World Orienteering-in-Schools Day"