The Shulhan Aruch (Orah Haim 429:2) writes that during the month of Nissan, one does not recite Tahanun, “Tzidkatecha” or eulogies and public fasts are not announced, as the month has a joyous character.
Regarding visiting cemeteries during Nissan, there appears to have been two customs in Morocco. Rabbi Shalom Messas (Shemesh Umagen, vol. IV, Orah Haim, § 66) writes that there was a custom to visit cemeteries where people would recite Tehillim and hold Seudot Mitzvah in memory of the departed, many communities would even visit cemeteries during Hol HaMoed since it would bring spiritual satisfaction to the departed (particularly in the city of Rabat).
On the other hand, Rabbi Yosef Messas (Mayim Haim, vol. II, § 132) writes that there were communities, in which people would not visit cemeteries during Nissan, and so was the custom in Fes. This is based on the Arizal (Sha’ar Hakavnot, Sha’ar Ruah Hakodesh), that one should not visit cemeteries during Nissan. However, many would still visit the grave site of a prominent rabbi.[c.f Ben Ish Hai (Parashat Vayeshev) who writes that although one should not visit a cemetery on the anniversary of the passing of a relative should it fall on Hanukkah, Purim etc., there was a custom in Baghdad to visit the graves of prominent rabbis even if it fell on those days].
During the first two weeks of Nissan, there is also a custom to recite Parashat HaNesi’im (Bamidbar 7:1-89) in commemoration of the Mishkan, which was inaugurated in Nissan. Additionally, the Rama (Orah Haim 429:1) writes that there is a custom to provide wheat to the needy so that they may bake their Matza. Nowadays it is more practical to give Ma’ot Hitim, that is, money to the poor for their Pesah needs. Since there is no obligation to donate money for Ma’ot Hitim, one may use one’s Ma’aser money for it.
Summary: If one has a custom to visit cemeteries during Nissan, one may do so. One may visit the grave site of a prominent rabbi during Nissan. It is a worthy Mitzvah to donate Ma’ot Hitim funds to the poor to provide for them for Pesah.