There was never any reason to suggest that Lily and James and the rest of the crew would be excluded from hogwart's Christmas season, so I think it's safe to assume they at least celebrated, in some way, shape, or form, Christmas.
Now Easter I'm not certain, I don't recall the books ever mentioning Easter, but I've been wrong on many occasion before.
Now I think Hannukuh and those holidays are out the question. My reasoning is(don't be offended or anything but.....) People who are not religous(as wizards don't appear to be) tend to celebrate Christmas in wintertime if they celebrate any holiday at all. Plus the fact I know for certain no Jewish or any other holidays except Christmas and a few others have ever been mentioned in the books.

Julie