F.H.
Hi C.-
I grew up semi-bilingual (my grandparents lived in Mexico and we had a Spanish only- monolingual- nanny.) I did not study any foreign language until French in HS, then one year of Spanish in College. The early Spanish developed my ear for the French, making it easier. Early immersion is great. It provides one with an authentic accent, much intuitive grammar and wires the brain in beneficial ways.
BUT, It is a BIG commitment, both tuition, time and effort (on your part.) In order for it really to work you need to have ongoing exposure and motivational buy-in on the part of the child. It has to be FUN, relevent and required. Dance, sing, make it a game. A good immersion school can do that. A community that speaks the target language can do that. An Au pair or foreign exchange student in your house can help.
If you do not speak the language it is very hard. I have my 4.5 year old girl in both a Spanish and mandarin immersion program. (Not full time school.) Yes, I am a bit crazy. She has had Spanish exposure from birth (mine is a bit creative, so I feel the need to have outside instruction) and started mandarin last April.
Frankly, my expectations for the Mandarin are pretty low: I want to develop her ear for the tones, so that she can study it later if she wants to. I feel it is THE language to know in 20 years. The biggest hurdle for me is my inability to read it. Pinion makes no sense to me. Personally, I would not both with French unless you have a good reason, like you visit relatives in France every year or two.
In my experience, you have to search out supplementary material and learn some degree of it yourself too. (I can now count in mandarin.) Audio/visual materials are best. They can learn to read later. The point at this age is to learn it the way they learned English: through hearing it, constantly. They say that you need at least 4 hour a week, minimum, to improve at something. I would say strive for it being something you do every day, for say 1/2 hour. Just part of the routine. Like you always listen to it in the car. (Like I said it is a commitment from you too.)
There are some, like the "teach me" series: www.teachmetapes.com available through the Marin library system. Look for songs/audio dialog with the words printed in both the language and English. If you succeed with the basics, later you will be able to watch some DVDs in the target language (dubbed.)
If you have cable (we don't) you can check out "NiHao KaiLan" in Nick Jr. You will have to try different programs to see if they fit your child. And to mix it up and keep it interesting. My daughter likes the "Follow Jade" video but not the "...With Mei Mei" Frankly, they are pretty similar. Go figure. I like Language Tree's DVD. All three are in the library system. Also check the website ChinaSprout. (Have not bough anything from them yet, but they seem the most comprehensive I've yet found for young child mandarin.) There is more in San Francisco's library system, but make sure it is not Cantonese.
For French try Berlitz Jr., any picture dictionaries (Osborne has a good one, I think they have it at the Discovery Museum store) Ask the librarian or the bookstore to do a search for you. You can also search Amazon for people's recommendations. I also still like the "Baby's First Words in..." music CDs, even at 4. You can do advanced searches on Marinet (library) by language.
BBC's Muzzy is also available through the Marin library system. I am not too wild about Muzzy, personally, as I do not like some of the stereotypes it reinforces. Remember content is important too.
Last thing. I am pretty strict on limiting video/tv time, but much more willing if it is in a foreign language! Good luck!