Something young children do more than almost any other age group is create. They master new skills very frequently, integrate the skills into their everyday lives, and are soon creating things of striking originality. Something I try to do in each of my lessons is have a student create something new, something to express their musical thoughts.
I mostly do this through improvisation at the piano. Even at the first lesson, the student and I discover high sounds, low sounds, how they differ from each other, and how they make us feel. This is all the information we need to create our own original piece of music! It is usually a duet, but sometimes the student cannot wait to be the sole performer of their new song.
Exploiting high and low sounds, the groups of 2 and 3 black keys, fast and slow, loud and soft are all great for beginning improvisations. But this strategy also works for more advanced concepts like scales, chord progressions, and interval recognition. Just last week, a student and I took some time in a lesson to improvise a piece in an unfamiliar key (B Major) to help facilitate the learning of her next piece. Seeing the notes of that scale on the keyboard and hearing how they functioned and interacted with each other really helped her confidence once she started practicing her piece.
Try some improvising with your students (and maybe yourself as well) and see what you can create!