My son and I have been to two of these events. I would echo everything buff81 says, and add a couple of things which may be unique to our area (Michigan):
-ROTC was also presented at our events, with both cadets and cadre present to promote the program and answer questions
-at the fall one we attended, applicants in their senior year were also invited to do a brief interview with an admissions rep from West Point. I don't believe these were scheduled in advance. In my opinion it would be good to be mentally prepared for this possibility, and to have a resume just in case
These events were very positive and inspirational. Not a lot of new information, but worthwhile nonetheless.