In 2001 a group of students and young professionals had the same idea about space: it needed a FUN holiday (something more than a 'space education week') every year to get people inspired and motivated. They chose April 12 as it was the dual anniversary of the first flight of a human into space (Yuri Gagarin in 1961) and the first launch of the US Space Shuttle program (STS-1 aboard Columbia in 1981). They named their event Yuri's Night and have been celebrating ever since.
Yuri's Night events have been held on all seven continents and even aboard the international space station in orbit above the planet! The holiday organizers followed your same approach: give up control. The logo and name are available to anyone, anywhere that wants to host a celebration. Anyone on the planet can also register an event and have it publicized on a global map.
Great job putting together a how-to for making events with an impact!