As others have said, beware of "dropping off" your DS/DD alone (i.e., without a family member/friend sticking with him/her). If left alone, they will quickly be swallowed up into the process and, by the time you return, they will be long gone, not to be seen again until the end of the day. Thus, be sure to leave at least one family member with the plebe-to-be. Or, as others have advised, take the shuttle bus, which keeps everyone together.
There are tons of places to drop the kids off on the yard, not just Alumni Hall. Pick a spot away from it, meet there and then go to Alumni. If there is no one in your travel party with movement difficulties just all ride the bus.