I had to make a big decision like this a couple months ago. I informed my immediate boss and team leader personally before I sent the email out to all the 'official' people.

You've been working with your boss and team leader for quite some time now, so it's only fair that you tell them that you're leaving, that you've made your mind up (to avoid persuasion to stay), and that you wanted to let them know before you sent the email out.