My first advice would be to hire a clown, since I am one. A clown could face paint, twist balloons, put on a magic show and do other fun things. I don't know where you live, but if you happen to be in central Iowa, check for "Clowning Around" in the phone book and on-line. But aside from that, here are a few things I would suggest. (I also taught arts & crafts after school for 12 years.)
1. Activity Time: If you have any kind of rhythm instruments or could make some fun ones using your imagination, that age loves to have a parade. You could sing Frosty the Snowman or whatever, or play something from a CD as you march around.
2. Craft Time: There are lots of fun ways to make a snowman out of paper. One way would be to make separate parts of the snowman for them to cut out. Have them cut out two pattern pieces for each body part, but in two colors. (Or you could pre-cut them.) Lie one color down with a little space between each part, but aligned as a snowman. Place a piece of string vertically, taping it to the three circle pieces and hat (leaving about a half inch between each of the circles for the string to be visible, and with the hat piece overlapping the head circle). Now paste or glue the other colored pieces on top of the first pieces. Add buttons (3 small for middle torso and 2 on bottom circle) Have the kids draw on his face with crayons or whatever, add a ribboned bow tie around the string between the head and torso, and the string length extended beyond the hat should be long enough to tie a nice sized loop to hang from the tree or the wall. Make one yourself ahead of time, so the children can see it, as they put their own together, and also so you can more easily explain how to do it.
3. Game Time: Play fruit basket upset, but instead of one person being eliminated from the game each time, have the one who doesn't get a chair in the circle (with everyone facing in) stand in the middle of the circle ready to find a seat the next time the music is played and then stopped. So there's always someone in the middle of a circle of chairs filled with other children. It just keeps going until you want the game to stop. Children love this and there are no hurt feelings. Frosty the Snowman could be played with you or another adult doing the starting and stopping.
4. Refreshments Time: You could continue the theme of the snowman by making a snowman cake, or cupcakes for them to decorate themselves. Miniature muffin pans could be used giving three to each child for them to make a three tiered snowman on their plate (with the bottom of each cupcake placed on the plate, so you are looking down at the finished snowman) with a half a round cookie for the hat and a marshmellow for the top of the hat. For less mess, you could put white frosting on all the miniature cupcakes and then have them finish the decorating with red hots for the eyes and mouth; a piece of orange colored coconut for the nose, (using a toothpick to apply it) and miniature M&Ms for the buttons. Take a picture of each child with their snowman on the plate and then it's time to eat them with whatever else you want to add.
V. Garrett (or Trixy the Clown)