Back on-topic. Nothing wrong with a trip (particularly an expensive trip) being the main presents for the year. There's also nothing wrong with picking up small souvenirs of a few places the kids really liked that will remind them of this trip--and those can be the "official" presents. Imagine on Christmas Day (well, I'm not Christian, but I'm imagining) that as each kid opens the little presents, the family can relive the vacation.
That's as long as the memories relived are not ones belittling a person, as in, "Remember when Johnny's pants fell down in front of Buckingham Palace?" Parents should not do that nor should they allow siblings to do that.