M.S.
Have an un-Halloween party! No costumes allowed! Since Halloween is on Friday this year, I suggest having her party the next day. Do whatever she likes - tea party, princess party, Curious George, old fashioned one with musical chairs, etc - let her help decide. For my oldest daughter's 5th, we just rented a space in the park, brought food and a cake, and let the kids play in the playground. It was great! Good luck to you and happy birthday to your daughter!