Halloween isn't just for kids. Adults can have fun too! www.funshop.com is a place where adults can order a costume for themselves. Join your kids and dress up!
Check out http://www.buycostumes.com/ for other dress up choices.
If you aren't taking the kids out for trick or treat, there are options for you. Decorate your house to be the scariest in the neighborhood! http://www.halloweenmagazine.com/decorations.html
You can't forget Halloween themed food: http://southernfood.about.com/library/holiday/blhwidx.htm
Most importantly, if you are out with kids, be safe: http://www.allhallowseve.com/safety/index.html