We have done Christmas away from our house since our kids were 3 and 4. We moved about 700 miles from our families due to job transfer, and always go to the families on Christmas.
The first year, we just had "christmas" the day we left. The kids didn't know it was really the 24th, they couldn't read a calendar yet.
For several years after that, we took one special present to grandparents, and "Santa" (had great neighbors!) left the rest for when we came home. Explained to the kids that Santa knew we were at Grandparents, and couldn't fit all our things in our car for the trip.
Now they're 10 and 11, and we do some before we go, and some when we come back.
We're also on the 2004 Christmas cruise, and since it's our main gift for that year (this year too!) we probably won't have that many gifts to give. The kids are already prepped that the cruise is the majority of our gifts to each other for the next 1 1/2 years.