If you or your wife gets naturalized before your daughter turns 18, you can apply for a passport for her at any time after that point (you can do it right away or 10 years later, or whenever, it'll be up to you). Her age at the time of applying for passport is irrelevant. However she must not apply for a passport before becoming a U.S. citizen.
To get your daughter her first passport, you and your wife will need to come to the passport application facility (usually at a post office) with your daughter, bring your marriage certificate, your daughter's birth certificate, your daughter's green card, and the naturalization certificate of at least one of the parents.
This will be sufficient for your daughter to be issued a passport, provided the date on the naturalization certificate of at least one of the parents is earlier than the date of your daughter's 18th birthday.
I would also suggest that when you and your wife submit your N-400 applications, you enclose a cover letter asking for expedited processing. Explain in the letter that your daughter is soon turning 18 and that you would like to be naturalized before that happens, so that your daughter does not age out of deriving automatic citizenship under the Child Citizenship Act. As far as I know, USCIS does consider the age-out situation like yours to be a valid reason for expediting N-400 applications.