You're not missing out too much.
essentially o week is this: socializing with people, socializing with people while drinking, getting a tour of the uni, joining clubs/societies, scabbing free stuff
the first two can be done during the rest of the year, the third you'll learn as you go, the fourth not 100% necessary and if you know someone in the club/try heard enough you'll be able to join the club anyway, the fifth, fun, but not really too important in the grand scheme of things.
I wouldn't stress too much about missing o-week tbh.
In terms of AAD, it's basically where you go into the uni and get some advice about subjects to do. Can be useful if you're unsure of what subjects you want to do and want to talk to someone, but if you're prepared to do some research and go through the handbook, not necessary.