Tertullian, the only example we have of someone who believed children and infants shouldn't be baptized from the Patristic period, doesn't deny the efficacy of Baptism, just the opposite. It is because Tertullian believes Baptism is efficacious for infants and children that he says it shouldn't be done--because Tertullian considers sins committed after Baptism as risking one's soul to hell, and thus Baptism should be postponed for as long as possible. Tertullian also recognizes the baptism of infants and children as an ancient and common practice in his own time.
"And so, according to the circumstances and disposition, and even age, of each individual, the delay of baptism is preferable; principally, however, in the case of little children. For why is it necessary— if (baptism itself) is not so necessary — that the sponsors likewise should be thrust into danger? Who both themselves, by reason of mortality, may fail to fulfil their promises, and may be disappointed by the development of an evil disposition, in those for whom they stood? The Lord does indeed say, "Forbid them not to come unto me." Let them "come," then, while they are growing up; let them "come" while they are learning, while they are learning whither to come; let them become Christians when they have become able to know Christ. Why does the innocent period of life hasten to the "remission of sins?" More caution will be exercised in worldly matters: so that one who is not trusted with earthly substance is trusted with divine! Let them know how to "ask" for salvation, that you may seem (at least) to have given "to him that asks." For no less cause must the unwedded also be deferred— in whom the ground of temptation is prepared, alike in such as never were wedded by means of their maturity, and in the widowed by means of their freedom— until they either marry, or else be more fully strengthened for continence. If any understand the weighty import of baptism, they will fear its reception more than its delay: sound faith is secure of salvation." - Tertullian, On Baptism, ch. 18
And, further, Patristic sources readily acknowledge infants and young children as being joined to the Church,
"For He came to save all through means of Himself--all, I say, who through Him are born again to God--infants, and children, and boys, and youths, and old men." - St. Irenaeus, Against Heresies, Book 2, ch. 22:4
"And they shall baptize the little children first. And if they can answer for themselves, let them answer. But if they cannot, let their parents answer or someone from their family." - St. Hippolytus of Rome, Apostolic Tradition, 21
"Therefore children are also baptized." - Origen, Homily on Luke, XIV
"For this reason, moreover, the Church received from the apostles the tradition of baptizing infants too." - Origen, Homily on Romans, V:9
-CryptoLutheran