I never put it on for any minhag, though I did put it on them for their brissim. I just reasoned that the sooner you accustom a child to something, the sooner that child will accept it as natural. My boys were so used to the idea that a kippah and whatever we used to keep it on, was part of them, they never balked at wearing it, neither did they pull it or the clips off, and they always kissed it and put it back on, if it fell off for some reason. My ainekel will NOT allow a kippah on his head, and he is kinehora two and a half. I won’t give my kids mussar about it, but it does bother me. YArmulke means Yarei Malkah (has awe of the King, Hashem). The kippah is a reminder to men to have that feeling of awe all the time.
It is SO easy to keep kashrus with young children, there is no excuse not to, IMO.