The presence and management of children at Mass is an issue that can generate more heat than light. I would like to tackle it here on the basis of a slightly deeper set of principles than is usual.
Full disclosure: I am a father of nine; my youngest has recently turned three. We have had to manage a child under five at Mass since our first was born in 2003; for most of the time, we’ve had two under five. That may sound extreme, but a couple who have three children at three-year intervals will have a child under five, and sometimes two of them, for fourteen years. This is a big chunk of your life.
The first question is whether bringing small children to Mass is good in principle. Children under the “age of reason” (usually about seven) are not bound by canon law to attend Mass. Often parents have no choice but to bring them in order to attend themselves. But supposing they had the choice—if they could attend different Masses, or leave the children with friends—is the ideal to bring them or leave them behind?