Not a lady, I know... But why don't you just put a lot of effort into making the moment you ask the question special, and let the rest of it fall into place as it should?
Is asking after dinner the best you could come up with? (And no, I don't mean to be derogatory...)
Me? I found a hotel, on a pier, in the middle of a river. She thought we were going to one location, but I took her to a different city (same general direction at first) outright.
Surprise is a good key element here. Ask her early in the trip, so that she can remember being engaged for the whole trip, not when it's ending. When you go walking, find a place that the two of you find special, return to it later with her, and ask her there.
Or, you could ask her before you even get on the plane...
"Well, then," the Cat went on, "you see a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."