I currently have one young child (2 years old) and another baby on the way. There are times when he will spend Saturday night with his grandparents and we will pick him up after Mass on Sunday. Sometimes it is nice for my wife and I to be able to focus on the whole Mass without constantly having to make sure that he is calm and not getting into trouble.
While going through a new examination of conscience, there was a question of whether or not I neglect to bring my children to Mass. My question is twofold: is it a sin for us to once in a while allow our toddler to miss Sunday Mass, and if so, at what age (or what level of development) would it become a sin?