You can leave pretty much everything in your room. There's an option to put stuff in security storage the day before OA; I was going to put my laptop there, but I missed the time that it was open, so I just left it in a drawer in my room and it was perfectly fine. The intensity of the outdoor experience for OA really varies, depending on the trip you take, but the bonding experience is really something worthwhile no matter what. You might complain during the trip, but afterwards they turn into memorable moments that you look back on.
Fun story: During my trip, we somehow managed to lose our trowel kit, so the Support Crew -- group of students sitting in nearby hotels delivering water, etc to you; if you get hurt or need to get evacuated, you get picked up by Support -- came to deliver us another one. (It was wonderful, we sat around eating all the food while the leaders went back to look for the trowel and then got in touch with Command Center.) We were trying to cross a busy road at the same time, but there were too many cars, so the two Support vans came in opposite directions, stopped, and put on their hazard lights so that we could pass. At that point, I couldn't stop smiling about how cool the Princeton community was.