In Australia we hold an event once a year called the Oxfam walk. Oxfam is an international aid organisation and as a fundraising thing each year they do a 100km non stop walk.

Its really quite inspiring seeing the teams come together and raise money for a good cause. Im sure in the States there is something similar you guys could do.

Another idea is an Advnture race. A TRUE adventure race. Think of it as a week long event where you try to complete multiple stages, mountain bike riding/canoeing/abseiling/trail running etc.

There is an international competition and they do events in most countries, but you could propose doing a crazy one in Ecuador or something they see some pretty amazing scenery.

One more idea - There is a trail in Spain called the way of St James. It is a Christian pilgrimage though I think just the history of doing the walk could be amazing. But theres some ideas