Hmm, no. You dont have to come to the uni at all during o-week it you dont want. That is of course it you want to miss out on all the fun. You dont have to go to any intro lectures, you can even go to the ones that dont apply to your degree, even bring your friends along, nobody minds, unless you made a noise, then you get kicked out.
Its fairly unlikely that your name will ever be called from a roll at uni, ever. Its big peoples world now, no one will be chasing you up for attendance to anything.