Obviously, we have no accord regarding pneumatology. That's pretty standard around here, from what I've seen and read.
So I will only say this: people, including children, have free wills. They can reach for God with all their heart, soul, and strength, and just as they are about to receive a touch from God, turn away, step back, and reject what was about to happen. It happens all the time, not just with receiving the Holy Spirit or speaking in tongues.
The baptism of the Holy Spirit is a gift given out of mercy by a loving Savior. It is never forced on anyone, ever. God doesn't operate like that. He is more than willing to give, and give, and keep giving, as long as faith in Him is present. People can reach out to receive, and receive, and receive, but draw away at the last moment.
This is obvious in all aspects of life. I can almost type ____, and change my mind last second, and not type it. I can almost say ____, and not say it, saying something else instead. I can reach out to receive a gift from someone at Christmas time or on my birthday, and pull back last minute, deciding I don't want it, letting it fall to the floor. I can almost take a bite out of a piece of food, and stop short when someone yells "Stop, the dog was on the table licking that before you came into the room"!
I can almost receive the Gospel and at the last minute, decide against giving my life to the Lord. I can think about repenting, and be on the verge of confessing my sins to God, and then hold up, and not do so. I can be
this close to getting into the water and being baptized, and change my mind.
Just as a man or a woman can literally run from the altar a second after they've been asked to say "I do", and so, not marry, so, too can a person, even a child, for whatever reason, run from the Holy Spirit a second after God first moves on them in order to baptize them.
Did that person almost get married? Yes, almost, but not quite. Did that person almost receive the Holy Spirit, but didn't? Yes, almost. But not quite.
Did that person almost speak in tongues? Yes, but clamped up and refused to do so, for whatever reason, moments before they would have otherwise spoken in tongues. In that clamping up, since the Spirit is compared to living/running waters flowing out of one's side, it should be no surprise that when a person resists speaking in tongues, but still doesn't want to let go of the Spirit, either, that an impasse will occur at the point of entry, i.e. the mouth. This causes people to, for lack of a better word, stammer.
Should stammer be connected back to
Isaiah 28:11-12? Someone else can argue over that. But
stammering, shaking, quivering, or whatever word/synonym one wants to use, is still something that happens, especially to kids. Is it in the Bible? No, but there is also no Bible that states a child ever received the Holy Spirit, and yet children all over the world receive the Holy Spirit constantly (while it is promised to children a la Acts 2:39, we read no actual account of it occurring, but know it must have and still does). So, looking in the Word for something and not finding it printed exactly as you want doesn't mean it's not legitimate or not from God.