In general I think there is nothing wrong with genetic screening. The value of understanding predisposed conditions could be life saving and I bet no one would argue with that point. Genetic engineering, though, is much different and has some gray areas. Briefly (and singularly) the prospect of super soldiers or other outlandish ideas are beyond the scope of our current genetic understanding and will not be addressed.
For the sake of sterility or overcoming found genetic diseases I would absolutely grant my support for this use (in not only my own children but in everyone's children). Unfortunately, the mechanisms to engineer the genome for good (in this case for circumventing the presence of genetic diseases) are identical to those that are bad. Bad here would refer to any genetic trait that would give an unnecessary advantage to a person over another. This area is very gray. Understanding of course that everyone has different attributes, some genetic, and that leads to ones individualism. If, though, you were able to engineer attributes into children you would artificially skew the population dynamics towards genetic engineering and that could be detrimental.
Consider a simple case of keeping up with the Jones' where their child is smarter, or taller, or blue where both parents have brown eyes and that these attributes came as a result of genetic engineering. Nothing here is life changing but you would be inclined to do the same for the same pure intentions. Somewhere down the road though non-genetically engineered children would be suffering trying to keep up with smarter, taller, blue eyed children. The movie Gatica popularized this idea. The movie over-dramatises the circumstances but the concept is pretty accurate.
Less is a concern the prospect for genetic engineering but more so the extent to which some people would be willing to take the idea. As a geneticist I can attest to the robust characteristics of DNA and the extent to which the genome is self-sufficient and should not be altered. Like mentioned before, the altering of predisposed conditions like childhood leukemia is a noble effort and should be pursued. There are issues that are beyond the scope of this article that include the way in which we have evolved ... not with genetic engineering. The body and the mechanisms with which is has to protect itself, to advance itself, etc where not built with the 'wild card' of genetic engineering and we could very quickly find ourselves in an unrecoverable situation. Finally there are disadvantages to modifying genomes to overcome certain diseases ... other diseases (new ones) will pop up that will also have to be addressed. Late stage Alzheimer's did not exists 50 years ago. People did not live long enough to experience it. As we become a healthier species new diseases find opportunities and exploit them.
In conclusions I think genetic screening is a very valuable tool. Genetic engineering is also valuable and can be used for the betterment of humanity as a health tool. Very strict and strong oversight would have to accompany the process, regulations would have to be employed. Bio-ethics, informatics and genetic scientists would have to study the effects of engineering on the good of the population as a whole. All that considered it is still worth pursuing while heartedly.