I attended a Bar Mitzvah last night, and there was so-called "sefira music" playing, and there was also dancing. As far as I recall learning, there are some justifications for listening to such music, but I don't know of any heter to dance during Sefira. There were some local Rabbis in attendance, and no-one said anything, leading me to believe there is a heter for it.
My question is, what is the heter to dance at a Bar Mitzvah celebration during Sefira?