For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call. -- Acts 2:39 (KJV)
Peter had given the answer: repent, be baptized in the name of Jesus Christ, and receive the gift of the Holy Ghost. Then he widened the listener's view. The promise reached beyond the edge of that crowd in Jerusalem.
It named their children.
A Promise With Reach
Joel had seen the day from far away: "I will pour out of my Spirit upon all flesh." Peter watched that promise land in the street, then spoke as if no generation had permission to lock it away.
The same God who walked with Adam, filled the tabernacle with glory, and came in flesh as Jesus now poured His Spirit into people. Pentecost showed the Lord moving closer than anyone in Jerusalem expected.
That closeness reaches farther than the first hearers. Peter named children, distant people, and as many as the Lord our God shall call. Time cannot age that sentence. Geography cannot weaken it.
Say It Plainly
Children need adults who believe the promise belongs to them. A small heart can repent. A young mouth can call on the name of Jesus. A child can receive the Holy Ghost because Peter said the promise includes them.
Ask what you need settled in your own mouth before you speak it to someone else. Can you say Acts 2:38 with courage, mercy, and no apology? Can you tell a child, a friend, or a weary adult that Jesus has made a way for them to obey and receive?
The promise has names in it. Say them without fear.