From the iBooks Author: Publishing and distribution FAQ:
If a fee is charged for the work and it is in the .ibooks format, the work may only be sold through the iBookstore. If the work is in a different format, such as PDF or ePub, this restriction does not apply.
You cannot charge a fee for the book if you distribute it outside the iBookstore without being in violation of the IBA license.
The question is whether giving the iBooks file away as a "complimentary gift" while charging at your "design rate for the time it took to create the iBook" would be considered as having sold a book that you are not distributing through the iBookstore.
Using common sense, I doubt that Apple would object to this, seeing that a wedding book is of interest to only a very limited audience. Unfortuntely, common sense doesn't apply. What applies instead are the the license terms.
I would take the IBA EULA to a lawyer and get an opinion, if you want to be on the safe side. Pragmatically, the cost of prosecuting you for a license violation will cost Apple far more than all the revenue you will ever make from wedding albums. But that hasn't stopped some organizations, such as RIAA, from prosecuting similar breaches. If you happen to be the unfortunate one Apple decide to make an example of, you might regret it…
Michi.