I would have to say that....
Since Homosexuality is a sin, I would let my child know that it is a sin. It doesn't mean that I would love my child any less, but I as a Christian don't have to condone, accept or promote their lifestyle, and it would be unscriptural to do so. Many say that homosexuality is a lifestyle which one is predisposed to at birth through genetics. I find no evidence to support this, as many who have had these "predispositions" through genetics have changed from homosexuals to heterosexuals through God's grace and power. Also, the same about people being predisposed through "the atmosphere in which they were raised". Again...there is no proof, and the same answer stands here. It is a CHOSEN lifestyle, whether through ignorance or by free will, it is still a chosen lifestyle, just as turning from it and living for Christ is a chosen lifestyle.
Kudos!