I got some books to post and one of them is a children's book that is supposed to have a cd with it but it didn't come with it.  Can I still post the book?

No, you cannot post it.

From the Help Documents:

Books that originally came with accompanying media Materials: Yes IF the accompanying materials are included

• A book with accompanying audiocassettes (for example) will earn 1 credit.
• A book with accompanying cassettes or CDs is not an "audiobook".  An audiobook is a book read aloud by a narrator.
• If the listing for the book indicates that the book comes with accompanying media materials (CD, VHS, cassette, DVD), all materials must be posted with the book.  If you do not have the accompanying materials, the book cannot be posted alone.
• The accompanying media materials (without the book) also cannot be posted alone.

You can post it wiithout an ISBN, as a  custom listinng, making it clear that it's just the book. To do that, go to the "Post Books" page, find the option to post a book without an ISBN, and  create your own listing.