I say have a Crayola party. Either do what the poster said from above with coloring the boxes, or print coloring pages off the internet. You could make your own playdoh and let the kids make stuff with that for awhile.
Have simple games such as musical chair and hot potato and then give them crayola prizes like paints, markers, smocks, glue and playdoh.
For food I would have each kid make their own pizza. Supply fun toppings such as hot dogs
For dessert they could decorate their own cookies, ice cream sundaes or cupcakes.
For the treat bags each kid could get a 8 pack of crayons and a coloring book.
Toys R Us has their own crayola section so you can buy all the stuff there.
If you are looking for a birthday presents for your child here is an idea.
http://www.crayolastore.com/product_detail.asp?T1=CRA+5003-01
For the cake you can get crayon candles and just make the cake red, yellow, green and blue.
Get some balloons too kids always love them.