Yeah, as with Twik, the setup of the wedding does strike me as a bit odd, if they're not even planning on paying for a single meal for the people who came all the way from another country to attend their wedding. But if that doesn't bother you, that's fine.
I think I would feel odd not giving them anything
for their wedding. I do think, as a yes/no question, one ought to give a gift if one attends a wedding; but exactly what and how much it costs are influenced by so many things these days. You're probably spending a few thousand dollars on the trip, right? But if they were getting married next door to where you live, you probably wouldn't give them a gift worth
several thousand dollars, so it's not like the goal is to balance everything out.
Actually, I do
like cards, with a longish, personalized message written in them--some fond memories of the HC, for example. Sure, I could say those same things in person, but then the moment fades. For me, the written card is something to go back and look at whenever I want. Of course, other people don't like to keep cards no matter what, so it kind of depends on their personalities. In this situation a card like that is my first instinct--personal and warm, but small and easy to pack in their suitcase. Also, if they're getting married in their hotel room, they can accept the card and leave it there before everyone goes out on the town, so they won't have to carry it around all evening.
I also like the idea of photos--you could put together a photo album of the trip for them and mail it to them later. It might make a nice thing to sit on the coffee table that people can browse through, especially if you took the time to capture a lot of fun moments from the event.
Or some other souvenir from the trip, though I would have to think through the logistics first--am I going to buy something in Vegas, take it back to AU with me, then
mail it to them? That seems awkward. Or, if I buy it for them right there in Vegas, now they
have to carry it back home. And if I can buy it online and have it shipped directly to them, it seems like it kind of loses its shine as something you can only buy in Vegas, you know? But sometimes I think too much about these things.
Just don't cart a blender or a toaster all the way to Vegas, and then expect them to carry it home!