Unless you're traveling with very small children, take the big suitcases. You're a big enough group that you'll need larger transportation options (Uber xl instead of regular for example), so that won't factor in. This way you don't have to try and travel as light as possible, and you have room for anything you might want to purchase on the trip. Personally, as a duo, I take three suit cases, but i admit that's out of sheer laziness.