In Matthew’s account of Palm Sunday, it makes note of the fact that children were present for Jesus’ triumphal entry. And they were participating. In fact, as Matthew records it, it was the children’s shouts of "Hosanna" that bother the Jewish leaders.
But Jesus shows, as he does so often, that he wants to be associated with the children. He wants to be with them, he wants them to believe in him, he wants them to acknowledge him, he wants them to be fed with his Word. Did these children completely understand what they were saying? Maybe not. But that doesn’t seem to bother Jesus. He knew what they were doing. And more importantly, he knew what he was doing for them and in them. And even today, Jesus knows what he is doing in the hearts of the children who hear his Word and he wants to receive their shouts of praise.