Sometimes they send us from merkaz ha gerut in Efrat people who are going to make conversion in the next months. When I say kidush in Shabbath, may I give to them the cup of wine after the benediction? and if there are other jewish guests?If not, how to keep derech eretz with them?

Make sure you use “Mevushal” wine, as most wines are; it will not be an issue then.