I have the pleasure of working with this age group once a week. I think the biggest things to remember is that no matter what task you give them, in the end it will only come out as they want it to, and you'll be doing great to have their full attention for all of 10 minutes. For example, I asked my Wednesday night group to draw things they were thankful for and at least two of them drew cartoon characters, while still another one drew a picture of himself as an alien. At this age they're less concerned with actually learning a skill, and more interested in being entertained.
Remember ever making those Rorscach style paint butterflies as a kid, the ones where you glob paint in the middle of a piece of paper, fold it in half and mash it. This is a great way to teach this age group about the occurrence of primary colors creating secondary colors (that song from Blues Clues helps alot too, I've actually used this).
Coloring pages are absolute magic! The less than enthusiastic student usually will have no problem coloring instead of doing a project. Discussing with the kids who they might give the colored page to (like their mom, or their best friend) after they're finished helps them stay motivated.
edible projects are always awesome. You can teach how shapes can create structures with something as simple as a group aided gingerbread house. Not all kids will participate in group projects. Some kids at that age aren't quite adjusted to being around other kids yet, so have coloring pages or drawing alternatives available.
toy building tends to keep their interest as long as the project takes no less than 15-20 min to build. Paper airplanes you can fly outside, toy boats you can float in the sink, balls made from glue soaked string wrapped around a balloon are fun because after the glue dries they get to pop their own balloon.
When in doubt, pull out the plastic table cloth and model magic and or fingerpaint. Anything that will make a mess really attracts their attention. I keep around scrap Tshirt and those hair claw things to pull the back tighter to put over them in lieu of smocks, plus usually at the end of the year they like being able to paint their names on the shirts and take them home.
They're a tough group. You may need to get a helper to help lay down some ground rules so you can establish a routine. If you have the same kids each time eventually they'll figure out you mean business and will be more likely to pay attention.
If you ever need any specific project advice, please feel free to message me anytime
Hope this helps, hang in there.