Aww, try not to worry about the birthday blowout. I'm a firm believer in having a day off from the diet on your birthday! I certainly did anyway...
I could never do CD, like my food too much and I think it restricts you socially too. Of course it's effective for people but it seems all the people I know who have done it go round in this cycle of one week on the diet, lose some weight, binge on food and put all the weight back on, back on the diet and so on. You have to do what you think is the right thing but I think if you stick with WW, make a fresh start tomorrow and go at it 100% then I see no reason why you can't get back on track and have some good losses. CD would be a big step backwards now surely?
Anyway, good luck with whatever you decide.