Yes, it's ok. You'd say 'Good morning' or similar first, but there's nothing wrong with starting a speech in this way, It's fairly 'neutral' language - neither informal nor formal.

It's fine. You can say a few empty words like that so that people will notice you've started to speak. And it fits the pattern, "Tell them what you're going to say. Then say it. Then tell them what you said." But don't wait too long before saying something interesting. In a short course I took once, we were taught to begin with a "credibility statement"--something that gives you audience some reason to listen to you. For example: "Our boss asked me to fill you in on the the new procedures..." (Listen to me because our boss wants you to...) "I'm here to share what I've learned in ten years of growing tomatoes in this region..." (Listen to me because I've had ten years of experience...) "I used to have a problem avoiding buffer overflows in my code..." (Listen to me because I understand your problem...)

It is a normal way to start a speech, but a bit boring. Just start in with your topic. It will make the speech more interesting and engaging. Example: Internet security is not just about passwords anymore, there are many subjects that you need to keep in mind. . . . This is much more interesting than I am going to talk about Internet security. It is not just about. . . . Good luck in writing your speech.