gentile guests at seders

Question

May one invite,or as it sometimes happens, may let a gentile acquaintance invite himself to a seder. we know why they are interested, but it is an improvement over ritual murder charges that we kill their children to ouse their blood on peisach. these are the friendly enlighterend one 1. the intrinsic question is, can we have a goy at a seder 2. and as i recently discovered,,,, you cant cook on yomtov for a gentile, though it seems that that shouldnt apply for the first seder, when the cooking is done before yom tov