Lag BaOmer is a day of great Simcha, happiness. Normally, the day of the passing of a Tzadik is not necessarily a day of happiness; in this case, it is different, as Rabbi Shimon Bar Yochai himself asked that on the day of his passing, we should rejoice and celebrate. The restrictions of Sefirah are virtually non-existent on the day of Lag BaOmer amongst almost all groups of Yidden. Sefardim are particular to wait to lift the restrictions until the day after Lag BaOmer, and the Kabalah says that haircuts should not be taken on Lag BaOmer according to many opinions. Upshernishen for children certainly are done on Lag BaOmer, even those that are particular with the ways of Kabalah. It is ironic that some people shave davka on Lag BaOmer as a celebration of Rabbi Shimon Bar Yochai, when Rabbi Shimon Bar Yochai was particular about maintaining the TzelemElokim, the dignity of the human being created in Hashem’s Image, and with regard to a Yid, by wearing a full beard.