Vulcans do have emotions. In the movie Serak tells Spock that Vulcan emotions are stronger than that of most other species. In the past their strong emotions led them to be violent, and Surak's philosophies taught them to repress their emotions and control them, but those emotions are still there.
Sarek fell in love with Amanda, and after her death fell in love with Perrin. So he is obviously attracted to human women. Most people do have a "type" after all. He probably saw in Perrin many of the same qualities Amanda had.
Sarek is a very handsome, intelligent and charismatic man, it doesn't seem strange to me at all that Amanda fell in love with him.
Spock is supposed to be the first successful Vulcan/human hybrid child, but I don't know that anything was ever said about Sarek and Amanda being the first Vulcan/human couple. We know from Enterprise that T'Pol and Trip were involved but they didn't marry.
The Vulcan children clearly had not developed strong control of their emotions yet.