Q. Can someone order and place a matzeva on his and his wife’s kever while they are still alive? They are afraid that their children may not comply with their wishes. Can they also include their names?

A. It is an established tradition observed by many to acquire while alive a final resting place. Midrash (Vayikra Rabba 5: 5) quotes Rabi Eliezer that a person should have a foothold in the Bais Hakvaroth so he should merit to be buried there. This kever acquisition is not seen as a detrimental “siman” but rather an auspicious one. (See Maharam Mintz 18 and others.)
There are different minhagim in regards to the relationship of the kever-owner and his future burial place as far as visiting, praying or even inviting guest and offering a “tikun’ on site (See; Shaarei Yerushalaim p. 73, quoting the Tzava’ah of Rabi Yehuda HeChasid)
Poskim differ as far as the correctness of purchasing and placing a matzeva while one is alive. Tziun L’nefesh Chayo (21) quoted by Chaye Moshe (p. 269) permits even the inscription of the name.
Kuntres Eitz Chaim (Bobov ,6: p. 146, Birurey Halocho by Rav Chaim Rotter) mentions indeed this particular shaileh, in regards to individuals that cannot rely on their children for complying in a proper matzeva placement and prepare the stone including names and other inscriptions. He, like other Poskim, compares it to Avshalom’s matzeva erected while he was still alive. (Shmuel 2:18:18) However, he mentions that the Arizal would not permit placement of the matzeva.
Horav Shlomo Miller’s Shlit’a opinion is that while one can prepare the kever itself, the tachrichim one should avoid purchasing and inscribing the stone, as indeed Avshalom’s end was inauspicious.

Rabbi A. Bartfeld as advised by Horav Shlomo Miler Shlit”a