Yes; be polite to people. Also, I don't give money to people who act like they think they are one of the greatest Christians ever (that isn't necessarily directed at you; I don't remember seeing any of your posts except the two above. I'm just saying that people like that make me give my money to other groups
). Also, I wouldn't give any money to someone who condescended to me.
Also, I hope that you prayed about whether to go on either trip very carefully; I've seen tons of people go on mission trips just to get a fun vacation or be able to tell others that they had gone on a mission trip. Yes, even if they were going to be working the whole time.