Hello! Immersion is really the best option, but I think it would be extremely hard to create such conditions if you don't live in Russia. I know several families that live in Europe and one of the parents (mother or father) is Russian. Only a few children can hardly understand Russian, and they practically do not speak Russian.
I tried to teach myself English to my daughter when she was 3-4. I would not say it was useless, but it is really hard to motivate your own child to speak a foreign language :) And I saw a big diference in progress when she started to attend English courses for kids. She liked it very much since she contacted other children during lessons and she learned English much faster.
Well, to summarize, just in my opinion: if you (and your wife) are not Russian or do not live in Russia, it is better to find some Russian courses for children. Also, it would good if you can find some activities that would be funny or interesting for your child, and you can use Russian at that, like games or cartoons in Russian.