I don’t speak the language, but can I help my child learn it by using only DVDs, videos and books?
DVDs and videos alone won’t teach a language, but it certainly can’t harm to try. At best it will sensitize the child to foreign sounds and help him acquire a passive knowledge of the language. What might work better is actual interaction in the language, which might be a challenge if you cannot speak it yourself. Nevertheless, you want to introduce a third language. So what can you do? How about a language playgroup which is open to non-native speakers? Maybe creating a specific time each day when your child practices the language? Is there a language school in your town? I know a Korean language student who has everything in her house, furniture, walls, doors labeled with post-it notes to facilitate the learning of vocabulary: ‘This is a chair’ is stuck on the chair, etc. Just make sure that in your enthusiasm to “teach” another language you don’t lose your sense of play by setting your expectations too high!