A Gentile's deeds are judged by God mostly (indeed, almost completely) in regard to the person's intention, rather than the main focus being upon the specific deed itself (Seven Gates of Righteous Knowledge by Rabbi Weiner and Dr. Schulman, p 83, citing Tractates Rosh HaShanah 4a and Bava Batra 10b).
For Gentiles, Halloween and Xmas are fine if they are celebrated with no religious intention.