It's perfectly legitimate. It's fine to speak to your child in a language that is not the official language in the country you live in. It's obviously more help

It's perfectly legitimate. It's fine to speak to your child in a language that is not the official language in the country you live in. It's obviously more helpful if SOMEONE also speaks to the child in the official language, but that's besides the point. Klingon is a constructed language, but it is sufficiently complex to be generative enough for actual use. Constructed languages aren't evil or irrelevant either -- look at Esparanto, which has a substantial amount of native or fluent speakers (more so than some "real" dialects). Sapir-Whorf (heh, Worf) notwithstanding, we know that the "choice" of native language does not affect the child's cognitive capabilities negatively in any way (basically, as all languages are generative, you can express everything in any language -- if you lack the words, you make them up). It's unusual, but it's hardly something to get your panties in a bunch over. There's no difference between speaking to your child in Klingon or any other minority language, constructed or natural. That's the beauty of it. The human mind is quite adaptive when it comes to utilizing language.