Isn't it better to wait until children can decide for themselves whether or not to be baptized?

No. We no more wait for our children to decide about being in the family of God than we wait for them to decide if they would like to be a part of our human family. As parents, we make many decisions — in matters of health, safety, education, for example — for our children. Of course, they may later reject what we have done for them. But, this possibility does not relieve us of the responsibility to do all that we can for them spiritually, as we do in other aspects of their lives.

From FAQs About Baptism, Membership, and Salvation

Learn more about baptism -
By Water and The Spirit
This is Your Baptismal Liturgy