A look of surprise at first, but then a smile. He'd had girls surprise kiss him before. He hadn't liked it most of the time, mostly because the kisses had been sloppy, tongue-invasive, and demanding, an attempt to get something he simply wasn't willing to share with them. Maxine had kissed him on the cheek as reaction and a show of gratitude, not as a manipulation or demand. So he quickly decided he liked it. She still seemed embarrassed though, and that was endearing.
So yes, his smile and eyes made his happiness pretty apparent. "You're welcome. I guess this means we can count our next meeting as another date then?"
Yes, he was very honest about his interest. If someone had tried to explain to him he needed to not show his interest so plainly, should wait between calls and feign indifference, he would have just been confused.