No way round actually buying a CD key for each of the games. Though it can be cheaper to get the Battle Chest Version. WoW + TBC + some crappy guide. This is I think quicker install too, as the previous versions came on CD (4x for WoW 3x for TBC IIRC), the battle chest versions come on DVD, I'm not sure about what patches ship with that version. However its worth shopping around, several high street retailers dropped the price of both WoW and TBC when battle chest shipped and I have heard that some people got both parts for less than Battle Chest version...

As for the bonus time either through scroll of resurrection (SoR) (how cool would those be in-game ) or through the referral program (RP), you get the bonus time on the account that you used to activate SoR/RP when the account is either activated for another month (SoR) or upgraded from a trial to a full game (RP).