Either way.
The little corner plugs, which Apple bizarrely calls "duck heads", are what the world travel adapter kit is: it comes with 6 of them that cover the whole world supposedly. This is a not terribly cheap option, but it's definitely the most elegant, and the safest.
Your second idea, of an adapter plug, also exists, and generally will work fine, but sometimes those adapters can't hold up the weight of an AC adapter and it'll fall down and come unplugged.
Another thing to remember is that a standard boombox or electric shaver cord (just a cord with the "figure 8" plug on one end and the local electric plug on the other) will fit into the adapter after unplugging the duck head. Those cords are easy to find wherever you go, so you could even consider just getting that cord once you arrive.
tooki