My, my, he has QUITE a grin on his face!!! I love it! If I saw someone smile like that in real life, I'd want to chat with him.
You did well with the lines around his mouth, and the shape of his eyes, both of which hint at a smile without even looking at his lips.
His hair almost looks like it was deliberately spiked...did he do it on purpose or did he just get up, take a shower, and then wipe his hair with a towel and let it dry? Either way, I think it's such a fun look!