My undergrad degree is in linguistics. I studied a bit of second language acquisition. I don't mean to rain on your parade, but kids don't "learn" languages, they "acquire" them through immersion. That means consistent influence with a native speaker. If you are not already bilingual and cannot provide an immersion atmosphere (where even the nuances of language are learned), it just won't work.
A good book to read if you're interested is "The Bilingual Family" (can't remember the author now). We are bilingual at home. Dh is not American... but even with him being a native speaker it's difficult to get dd to actually speak to him in L2. She replies in English, usually. We have her in language immersion school (this will be her 5th year) and her L3, which is not a language either dh nor I speak is as fluent as her English. She spends 8 hours a day, 9 months of the year in that environment, though.
If I were you, I would try to find an immersion school he can attend. I think they even have Montessori immersion schools. And forget the programs like Rosetta Stone. The best you can get with those is that he'd learn the basics, not become a fluent speaker. Sorry to be a party pooper, but it really requires native speakers to learn anything beyond "hello", "it's raining", "where is the toilet", "I'd like a coffee and croissant", etc. Good luck! (And that doesn't mean you still shouldn't learn a second language yourself!!)