So if you're not going to try to introduce them to interesting things now, when do you plan to do it?
My experience-- with my own kids and many others-- is that most food reluctance is transmitted from the parents to the kids. Kids don't know they're not supposed to like what other kids eat every day in other countries, so as long as it doesn't have eyeballs and has a certain fun factor (eg tortillas), why not push their envelopes a little? The great thing about being an aunt is precisely the fact that they're not your kids and you don't have to play by the rules and live with the consequences; take 'em somewhere weird and who knows what they may like?
Irazu would be a good choice, just be sure to order some plantains, if they eat nothing else, they'll eat that.