If my bar-mitzvah is on channukah do I have to make an extra “Shehecheyanu” on that night?
This is a very good question.
Shut Rivevos Efraim (Vol. 6, no. 368) writes about this question at length, and brings many sources concerning the question of a boy who becomes bar-mitzvah during the period of Sefiras Ha-Omer, and some who make the comparison with Chanukah.
His conclusion is that it is best not to make the Shehecheyanu blessing on the first day, and to wait until the bar-mitzvah before making the berachah.
If the boy did make Shehecheyanu on the first day, he rules that Shehecheyanu should be recited again at the time of the bar-mitzvah. However, I have seen other authorities rule that it is best to have a new fruit or new item of clothing, and to have this in mind when making the Shehecheyahu (see Arba’a Sefarim Niftachim, p. 26).
Note that on the day of the bar-mitzvah, the candles should only be lit after nightfall, and not at shekiyah.
Best wishes and mazel tov!