Keep it Clean
If you're planning an arts and crafts party, don't forget to make that message clear to the parents of the children invited. You don't want Sally showing up in her best party dress, only to see it ruined later with paints or markers. Make sure the kids wear clothes that can get stained, and offer them smocks.
If you're having this party in your own home, think carefully about what kinds of art supplies you'll be using. It's true that kids love glitter, but you don't want to find glitter in the nooks and crannies of your home for the rest of your life. Also, invest in washable markers and paints if you can. Your furniture will thank you.
Think about holding the party outside, too. Cleanup is much easier, and the kids can get sloppy without the adults panicking.