Hi, Emmie - I like cowboy songs, especially the silver screen cowboy songs that came from Tin Pan Alley. One of my favorites is Cole Porter's "Don't Fence Me In," but there are lots of other fun ones. They're usually really easy to sing, and lots of people in your audience will know at least the chorus.
I got my start singing at camp about 35 years ago, and I've been leading songs at campfires and similar gatherings ever since. I've found that it's best to sing songs with choruses that are easy to learn. Songbooks and songsheets take away from the fun, and make it feel more like you're in school. It's better to know ten songs well and sing them over and over again, rather than to have a hundred songs you don't know all that well. Slowly add songs to your repertoire. If you don't like a song a lot, don't bother with it. Sing new songs for friends first - don't try to learn songs in front of strangers.
If a song is a round or has different parts, get a volunteer to lead each part, while you handle the overall direction and help out the weakest group. Be careful not to try anything too complicated until you and your audience are ready for it.
Most importantly, make sure you have fun leading the singing. If you have fun, everybody else will, too.
-Joe Offer-

(I deleted your duplicate message with my magic "edit" button)