Q. See question above. Can one invite a prospective Ger who is already in the process of conversion to the Pesach Seder?
A. As mentioned on last question (3078), Gentiles in principle should not be invited to the Pesach Seder.
Chashukei Chemed (Pesachim 99b) quotes Siddur Yaavetz that the proclamation at the beginning of the Hagada: 'Kol dichfin yesei veyechol," is an invitation to the Gentile poor to enter and share with us, as the Halacha requires to give them food first, because of 'Darkei Sholom" or maintaining good relations and peace with all. The next sentence of "Kol Deitzrich" refers to the Jewish needy. He explains that it could be refering to food that does not have to cooked.
He also relates about a Godol that was approached by some foreign important diplomats with a request to partake with him in his Seder, and he did invite them. However, he mentions that Horav Eliashiv zt'l explained, that they probably did not stay for the meal.
As in the question above, Horav Shlomo Miller's Shlit'a opinion is that if you inform the guest before Yom Tov that you cannot cook anything special for him and he will be sharing with you the food already prepared, in need it is permitted.
The Rov added that the guest should not be given a kezais of the Afikomen.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit'a