We are making a bar mitzvah for our 2nd son with music and dancing. at our older son’s bar mitzvah last year, we had ladies dancing (behind a mechitza), where as the mother I danced with other women. Am I restricted from doing this at this son’s bar mitzvah because of Aveilus (I’m fairly certain if I don’t dance, there will be limited or no ladies dancing – something my mother in law (and other relatives) from a weaker background enjoyed at our last simcha).
Since you are in aveilus, and the minhag is that one does not go to simchos etc. nevertheless it is permitted for you to partake in the Bar mitzvah meal, since you are the mother of the Bar Mitzva boy. However being there for the dancing and music is not permitted for you at this time.
It isn’t easy, but you should know that, your not dancing at the Bar Mitzvah is a big zechus for your mother’s nesoma! The reason is as follows. One of the reasons (I don’t remember where I saw this) why the aveilus for a parent is so much longer than for other relatives, is because the child not only lost the relative, but since the child is now missing the mitzvah of kibbud av v’em. In truth a child can do a lot of kibbud av v’em after their parent had left the world, because your parent get a divided reward for every mitzvah that you do. Therefore every time you’re abstain from doing something during the aveilus year of your parent, that in itself is an honor to the parent, and a mitzvah of kibbud av v’em. Since you just did a mitzvah, not only does your parent have the honor that your are mourning for them, they also have the zechus of your mitzvah, something that they now appreciate tremendously.
Daas Sofrim 4-108 in the name of Zera Emes, Pnei Baruch 20-23 in the name of R. S. Z Auerbach zt”l.