When I was growing up holidays centered around the family table. We met at my grandparents and the family would extend to grandparents, parents, siblings, cousins, aunts, uncles, second cousins, and an assortment of people who were "family by choice" as well as those related by blood. It was a huge crowd. Often we would have 2 or sometimes 3 or 4 tables full of people. The babies were always seated at the main table. Along with the crystal and china and silver was a special place for the youngest members of the family. Did they dump the mashed potatoes on the table? Often. Did they understand that this was Christmas (or Easter, or Mother's day)? Not really, not then. They did know it was something special, extra special because we were all there and doing something different.
Eucharist is like that. We are all together doing something special, and it's important that we include even the youngest members of the family. They are part of this too, this family meal, hosted by Christ. Do they understand? Only a little bit. (How much to any of us really grasp in this encounter with Christ in communion?) But we are all here together, in God's house, eating a meal together. We can work on table manner as they grow up. For now, Let the little children come, we can scoot over and make room for them around the altar table.