They almost forgot how great kissing is. It stands to reason that what comes next is probably great too — and they won't know if they don't try, which is why this conversation happened in the first place. They could just as easily have ignored it forever.
They start smiling goofily when Michael's face comes up to theirs, so the first kiss is mostly teeth. Their arms go around his waist and pull him closer, half on top of them, two layers of very thin fabric separating their skin. It takes an enormous amount of effort to compose themself enough to kiss him back properly, their mouth open, inviting him in. There's not even a second of hesitation. They even find his morning breath charming; that might not still be true in ten years, but now it is.