i used to be quite OTT about the routine, but what i've learned from Tracy's books are that we can't become hostages to the routine (otherwise we'd all be doing gina ford!)
What we did last christmas, and will repeat this year, is to still do betsy's nighttime bath, books, milk routine and try to put her down at my in-laws at her normal time. if she doesn't want to go to sleep we will let her stay up until our planned time of leaving at 10pm. Last year she was 10 months and fell right asleep. This year I suspect she may not want to sleep, but she will do the minute the car pulls out the drive. Then we'll transfer her into her cot. It took about a day to get her back on her pattern, but like PP said, it's worth it.
We travel to the states 2 times a year and I always stress about the 5 hour time difference, yet Betsy always amazes me. Within 2 days she's on US time and doing her normal pattern to the day.