Thanks to the internet-age, we have access to hundreds of free printable coloring pages. You can go to this website or this one to find great Halloween coloring pages. There are many, many websites that provide these, so slip it into a Google search and choose what works for you. My kids wanted to color a jack-o-lantern first, so that's what we did!
Another favorite activity of my kids is creating a haunted house using some construction paper and Halloween stickers. I drew the house for them and let them go to work!