Is it permitted to invite non-Jews to eat at:
A) At your Shabbat table
B) At your Seder table
A) It is permitted to invite a non-Jew to be a guest at the Shabbat table.
B) If the first day of Pesach falls on a weekday, one may not invite a non-Jewish guest, because of a concern that you would perform a melachah for his sake. This is not a halachah in Seder night, but in Yom Tov in general. Therefore if Seder night falls on Shabbat, it would be permitted to invite a non-Jew. However, on a night when the special nature of the nation of Israel is singled out, one would have to think twice to ensure that it is appropriate (it might be), depending on individual circumstances.