I always thought that infant baptism was a covenant that the parents make to raise a child iin a Christian home. Confirmation is when the child accepts the baptism.
That’s exactly right.
Well, Confirmation is the sacrament that formalizes it. But that's not to say a Catholic who is baptized as an infant yet never confirmed is not really baptized. I'm in that situation and am absolutely, positively baptized. Believe me, I accept my baptism.
No, that is a common misunderstanding with no sound theological basis. It is a common misconception amongst Catholics of the Roman Rite because of the late age at which they are confirmed. Baptism has to do with cleansing the person from original sin and reclaiming them for God, the parents speak on behalf of the child, but they are not the one making the covenant. Catholic parents made a promise to raise their children as Catholics at the time of their Marriage, not at the time of the child's baptism.
Also, Confirmation has nothing to do with getting an opportunity to accept your baptism as an adult. The effect of the baptism of an infant is valid with or without the Confirmation. A person who has been validly baptized already belongs to Christ and need only ratify this by loving God and living in accordance with His law,
Confirmation is not a coming of age ceremony in which a person accepts Christ, it is a separate sacrament of initiation which strengthens the Christian, bestows additional graces, and seals the recipient with the Holy Ghost.
The point that Confirmation has nothing to do with giving a teenager the opportunity to ratify his infant baptism is illustrated by the fact that the Eastern Catholic Churches baptize AND confirm Catholics as infants, and these Confirmations are valid and licit even though the recipient is an infant.