With the big change in the religious outlook in contemporary world, gifts for baptism need not necessarily be like the gifts of yesteryears such as a silver cross or a lovely ivory box of Rosaries.
Grown up children don’t care much for gifts received in the childhood. They treasure gifts received only till they are 6 years old. Considering this, my suggestion for a gift on baptism day would be a guardian angel cross.
If children are repeatedly told stories of guardian angels by their parents, they would soon realize they are safe in the presence of a guardian angel cross. Some children, when they are grown up and have kids of their own, they would cherish to recount their beliefs in religious gifts.