Generally speaking, kids are very welcome, including babies, but the Church understands that staying quiet enough for everyone else to have a hope of hearing the Mass is not within the capacity of every child. The general policy is that we would love if you would bring them, they absolutely belong here. You are asked to do what you can to keep them reasonably quiet and to teach them reverence and proper appreciation that they are in a place of quiet before God, but if they get loud instead, we’ll cope with it. Normally, a parish without kids is a parish that is going to die.
On the other hand, if the ordeal of having your children at Mass with you is too much when they are little, they aren’t obliged to be there until they reach the age of reason. Whether you bring them or not before that age is within your judgement as a parent. You are allowed to base your decision both on your own spiritual welfare as well as theirs. As the airlines will tell you, you have to have your own oxygen flowing before you can help your child with his.
My kids stayed at home with their non-Catholic dad until they were five. In retrospect, that may have been a bit late to start them back (it did not work well at all when they were two!), but now they are 7th graders who love to altar serve and voluntarily go to daily Mass, so I guess it turned out OK! When we re-introduced them to Mass, we sat up front (provided they behaved) and made sure they had comfortable Sunday clothes, so that helped, too.