How to start a book with an event?

Definitely use their names. Just jump right in and make sure they act like the characters you've developed. You can spend time introducing them later to your reader. Think about Star Wars Episode IV: A New Hope. You're thinking "what's going on and who are these people? but it grabs your attention. Your reader doesn't have to know everything and it's fun to learn more about characters as the story progresses rather than a paragraph of exposition about each one.