Well, the best approach in this case is honesty. Giving your employer two weeks notice is the common courtesy that most are familiar with, but the truth of the matter is that you can leave whenever you want/need to. Tell your boss sooner rather than later, as that is the courteous thing to do (they will need to schedule accordingly once you leave). Explain to your current boss that you received a better off and it s something you can t turn down, but that you are willing to continue working until next Sunday.
Tell your boss, Thank you, it s been fun but I gotta run .