Tricky, on a base level, so long as the two parents are consenting then there's no problem. The problems start with the consequences, depending obviously on the kinds of modifications that have been made. As advances continue you are going to get an entirely new species of human, many people call this 'Homo Superior' and this new species will eventually dominate us, and Homo Sapiens itself may well die out over the next millennia.
That's why there's so many rules and regulations and ethical dilemmas on this subject, and we're going to face a very similar scenario when it comes to Artificial Intelligence and bio-mechanical enhancement over the next couple of generations. I think one way or another we are in the closing days of Homo Sapiens as a species, unless an event happens which reduces our numbers and technological levels back several generations (ie asteroid impact, nuclear exchange, epidemic, etc).
I don't think there's any way to stop this from happening, and to be honest, it's questionable whether it should be stopped, this can be looked upon as just another part of the progression that started with the common ancestor many thousands of years ago and lead to evolutionary offshoots like the Neanderthal which eventually disappeared to leave us. Our last major competitor was the Neanderthal, and we helped to get rid of them and Superior will no doubt help to get rid of us.
After that...who can say.
Some level of technological and biological convergence? A transcendence beyond physical form? That's all real sci-fi stuff...but then again, so was a lot of the stuff around us right now.
