S.P.
Unfortunately if you really want him to know Spanish, a dvd/cd/book won't do the trick. My family is from Argentina and I grew up hearing Spanish constantly and can speak pretty fluently...my brother on the other hand learned from text books because the family had already learned English by the time he was born and is not so good at speaking Spanish.
On that note, my friends have used Rosetta Stone for the computer, and they are able to get by in general conversation, but on very basic levels. Your best bet is to expose him to as much of the language as possible as often as you can for him to truly pick it up.