Related for Pesachim 238:2

Rabbi Elazar ben Parta recited the words [of the Hallel] in a simple fashion [whereas] Rebbi would repeat his words (Y. Sukk. III.10.5). Rabbi Eliezer said, we grab the matzah for the children so that they don't fall asleep (Pes. 109a:1). Rabbi Yehudah says, even if he did not eaten [anything] except one appetizer, [and] even if he has not dipped [anything] except one [leaf of] lettuce, we grab the matzah for the children so that they don't fall asleep. How far does one recite [the Hallel, see Mish. 6:10]? Beit Shammai says, until "As a happy mother of children" (Psalms 113:9), and Beit Hillel says, until "[who turned the rock into a pool of water,] the flinty rock into a fountain" (Psalms 114:8), and he concludes with [the theme of] redemption. Said Beit Shammai to Beit Hillel, "But he had already completed the remembrance of the Exodus from Egypt!" (i.e., why would we conclude the Hallel with the crossing of the Red Sea (Psalm 114) if we have already recounted the entire Exodus?). Said Beit Hillel back to them, "even if he would wait until the rooster crows [to say Hallel], behold, [the Israelites] did not leave [Egypt] until six hours into the day, so how can we speak of the redemption when they have not yet been redeemed?" [With respect] to eating matzah, the bitter herb, and the haroset: Even if there is no charoset, the mitzvah [has been fulfilled]. Rabbi Eliezar ben Rabbi Tzadok says, "[It is indeed] a mitzvah [to eat charoset]. In the Temple, they would bring before him the body of the Paschal lamb." (Pes. 10:3.) [Presumably, he viewed the charoset as a substitute for the Paschal lamb, see Exodus 12:8.]

And they may not conclude the Pesach meal with an afikoman [a dessert or other foods eaten after the meal], like nuts and dates and parched corn. A person must engage in the laws of Pesach all night, even if it is just him with his son, even if it is just him by himself, and even if it is just him and his student.