These mini pumpkins are very inexpensive at pumpkins farms, but our grocery store also offers them as a kit that comes with some paint. Everything you need is right there in the package. If you get the pumpkins individually, acrylic paint should work fine.
Just give the kids (and adults!) some paint, brushes, sharpies or paint pens and let them come up with whatever design/pattern/faces they want. Fun for the whole family. And I also like the mini pumpkins early in the season because they don't rot as quickly as the bigger ones we carve every year.
Apologies for the wonky photos, they were taken while holding a 6 week old wiggly girl...
How do you like to decorate your pumpkins?