How about checking
http://cometchasing.skyhound.com/ ahead of time to see if there are any comets to check out. They are always in the sky and a 12" dob should be able to show several. While there may not be any with tails at the time they do tend to be beautiful jewels with a ball of gas around them. Often green when photographed so i think it may be a methane gas ball that starts to unfreeze early on its trip around the solar system before the tail starts to form as it nears the sun.
Something else that may be of interest is the main stars of the southern cross that most people are very familiar with. Show them how most are actually double stars not just one big bright star.
The magellanic clouds are a good target. If you brush up on your greek mythology the entire sky is full of constellations with stories to tell. Make sure to have a green laser pointer to help point out these things as you go.
Of course check on ISS flyovers too.
When you have an audience to keep from boredom the scope tends to not be the main point of interest. A friend of mine helped me get to a dark site where i could photograph andromeda. he started telling me about the story of andromeda in greek mythology and when I looked on the constellation chart I could immediately show him the same named relations in his story as they appear in the sky in relation to andromeda. blew him away , unravelled a sky chart is a huge tapestry of interacting characters. so while he couldn't appreciate the sky the way i did, he did connect with it in a way i couldn't.