While I'm not exactly bilingual, I would like to teach my children (when I have them) multiple languages, just because I think that the potential for learning (and especially for learning languages) is at its maximum during childhood.

However, I'm not quite sure what the best languages would be. I want to give them some exposure to a broad spectrum of languages. I know that the best way to learn a language is to actually use it. In this light, I'm wondering what the best balance between casually exposing them to a huge number of languages and learning them just one extra language really well would be.