The type of buttonhole really depends on the size of the band and the buttons. The yo buttonhole is certainly the easiest, and is stretchy enough for the buttons.
Since your button band is only 6 stitches wide, I'd do the yo one.
Just knit the first 3, bring the yarn to the front as if you are going to purl, then knit the next two together with the yarn in front. The yo will automatically happen as you wrap the k2tog stitches.