An infant cannot make cogent decisions and that is something that no one can do for him, even if they can take care of his physical needs.
As I said, they can teach him and encourage him in the right direction, but ultimately, the decision is his and always will be.
That's why God made parents. That's why kids obey parents and other authority figures in their lives who give them instruction, structure, discipline and protection to bring them up safely with the skills they need to be independent. At Confirmation, the person opts to declare for themselves. A parent is obliged to raise their child in their belief system, whatever that may be. Hopefully, they will do so without teaching them to resent anyone who believes differently...
**As I said, they can teach him and encourage him in the right direction, but ultimately, the decision is his and always will be.**
Exactly. Hence Confirmation.
As we mature in our lives and our Faith, we actively make a choice to keep that covenant begun at Baptism for the rest of our lives, at which point, we make our Confirmation. We receive the Holy Spirit in a special way. We also, having been given a name at Baptism when others spoke on our behalf, choose for ourselves a name of our own. From then on, we shoulder the responsibility to live for God through the tenets of that Faith.