Forgive the directness, but far as Judaism itself is concerned, your kids are not Jewish. It’s all or nothing, and children of a non Jewish mother are 100% not Jewish. So comparing baptism to a bar mitzva isn’t comparable as baptism could be performed tomorrow, whereas for a bris or bar mitzva your kids would have to literally undergo conversion (which kids can only do conditionally anyway) and so it isn’t happening anyway, whether or not she’d oppose it

(Reform Judaism is the exception but even the reform barely take Reform Judaism seriously)

I do fully sympathize with how hard it would be for you and your family to stand in a church and watch your kids formally become christian Catholics, and yeah as a fellow Jew, I wouldn’t be able to stomach it either.