I did a few admitted students days 2 years ago for law school (2 were at my expense while the other one was paid for by the school). Most schools make it an all-day (or at least all-afternoon) program.
Usually you'll end up getting a schedule of events. It'll include an introduction, a couple speeches by anyone ranging from professors, students, and alumni, maybe lunch, perhaps a mock class or a visit to an actual 1L class, they might split you off into concentration areas based on your interests (international law, environmental law, etc.), maybe they'll have a question and answer session with current students, discussions about financial aid, a tour of the campus, etc. Those are all things I had at my admitted student days.
As for getting away to see your parents, once the program is over, I don't see a problem with it (they might not miss you even if you do leave early). On my paid visit, I couldn't leave to see the city, because I didn't have transportation, but on my other two visits, I had friends with me so once the program was over, we toured the surrounding area.
Hope that helps a little.