I always planned an afternoon with some food, some activity and a creative project. One of the most succesfull was making a tea light holder out of a drinking glass and glass paint.
For this is bought some inexpensive glasses in a store. With foresight I could have bought some at a yardsale or saved empty mustard jars etc.
This is a photo of the one my daughter made when she was about 10-years old
After protecting my table top I gave each child a unopened tin can to put their glass on. They can use the can as a pedestel to put the glass on so they can turn their glasses bij turning their cans and don't have to touch the wet paint.I had them put their glasses upside down on the can so they could also paint the base.
Use the most inexpensive paintbrushes that you can find because the paint will ruin them.
You can also decorate glass plates with the stuff. When I did this I painted the underside.
This one I made years ago. I stood it on a window ledge so the light could shine through.
As you see there is a small piece of paint missing. I have found that after years of sunlight the paint may crack and flake off a bit.
Some plates and saucers have patterns impressed in them. You can use these as a guide as to where to paint.
The next one is well past it's prime but I still want to show it to you as an example.
Last year I made "tiffany" candle/tealight holder using glass paint and self adhesive lead tape.
I bought a very inexpensive glass vase but you could look in a yardsale or thriftstore. Then I drew the lines where I wanted to stick the tape on with a permanent fineliner and painted the areas in the colours I wanted. When the paint was completey dry I stuck on the lead tape.
This project is perhaps less suited for a childrens party because you have to wait untill the paint is dry before you can stick the tape on.
If you stick the lead tape on before you paint it makes the painting more difficult.
I hope I have inspired you!