Hi nileek,
I'm guessing that you don't know what any of the 10 different people prefer. Will this coffee be a gift?
Your best bet would be to stay with a medium roast. People who prefer dark roasted coffee can adjust to medium roast, but people who prefer medium roast have a very hard time drinking dark roasted coffee, because it tastes totally burnt to them.
Besides trying Colombian coffee, Ethiopian Yirgacheffe may be something that more than half of the 10 people should enjoy.
Rose