You are very wise to do that. We have two black cats and keeping them out of harm's way on Halloween is a ritual for us. Sadly there are quite a few sickies in this world that might like to get their hands on them for nefarious purposes.
Please, if you love your kittehs, keep them safe inside. If you have a cat(s) that already go outside get them fixed and vaccinated and DO try to keep them inside (some actually get used to it after awhile). If it's a new baby, keep it indoors, they will never know the difference. We should all do our part to protect these sweet gifts from God. kthxbye!