But we do know that God includes them in the covenant. We cannot presume that since we cannot see their hearts. Covenant baptism is not based upon presumption but the clear command of God to give the sign of His covenant to our children. If they don't, they will be covenant breakers and suffer the condemnation of old Israel. This means they are in covenant with God and have the obligation to repent of their sins, trust in Jesus Christ, and live faithfully before Him all their days.
Baptism is always efficacious.
It will either confirm our salvation or our damnation. To the contrary, it condemns him as a covenant-breaker. For the unrepentant, reprobate covenant child who has been given the sign and seal of the covenant, or for the adult who has later apostatized, baptism remains extremely powerful and significant. Over each reprobate head baptism seals and signifies the covenant of grace. But it is the negative aspects of the covenant with which the sinner has to do.