The precise dollar impact that the election for the $100,000 lifetime capital gains exemption will have on the various provisions mentioned in this question, such as the child tax benefit or the alternative minimum tax will depend on the number of people and the income and age characteristics of those who choose to use the election.
The election allows individuals to exempt up to $100,000 of capital gains. In most cases the cost associated with using the election will be relatively small compared to the potential tax savings of exempting capital gains. Nevertheless, it will be up to the individual to determine whether he or she wishes to utilize the election.