I agree that there may be a large generational component here. It has only occurred at some point since our parents' generation that adoption became "socially acceptable" and openly discussed outside the family, much less celebrated! Adoption was seen as a "second choice" for most people (and for some of us, perhaps at one time it was...) Accept and learn to love the kids, sure, but to celebrate their adoption and where they came from??!!! Oh Granny, turn over!!
Add to this the old "melting pot" picture of America. Anyone who came here was expected to make their ethnic roots "invisable". Recent immigrants to the States tend NOT to "melt" in, but retain their language and traditions proudly, and this still remains a bone of contention, particularly for many. (A friend from Canada once told me that there, immigrants make the country more of a "stew" than a melting pot, and that's the way everyone likes it!)
A vacation such as this is truly a celebration! Those of us who have gone through this process understand. We are blessed and indeed have much to celebrate! Others, sadly will never understand...
The devil in me wants you to send a copy of the vacation brochure to this lady's kids ...