i renewed my passport but if it doesn't come in time, i have my birth certificate as a back-up. i don't know if mine is worn out because its 30 years old but is it supposed to look like a really bad, poor quality xerox copy with the "seal" that is BARELY raised or indented that you cannot read what it says? haha!
If your renewed passport doesn't come back in time for your cruise, do you have your original expired one? I am not 100% sure on this one, but i think that you can use an expired passport as long as it is less than six-months expired. Otherwise, get a new birth certificate, you could run into problems with an old ratty worn-out one.