What's your question?
I have a couple friends that I eat lunch with and I'm the tallest one there. I feel uncomfortable when I tower over them. Should I slouch or straiten up? Do I tell my friends that I feel awkward?
Above all else, stand tall! Many people your age probably envy your height! Your friends like you for your personality. It doesn't matter what height you are; as long as you are a good friend to others, you don't have to try to hide your height.
Your friends probably know you feel awkward -- they might be feeling a little tension too. But you can't control your height, so telling your friends won't solve the problem of them being shorter than you. On the other hand, getting something off your chest can feel really good, and could help everyone feel a bit more comfortable knowing they aren't the only ones feeling a little different. Ultimately, it's up to you. Just remember: act natural, and stand tall!