M.M.
My daughter had surgery when she was 3 to remove a cyst in her throat. Very scarey. You are your son's barometer. He has no idea what to expect and has no reason to think it will be a bad or scarey thing. He will be watching you for clues on how he should be feeling about this. Even if you're nervous, you really need to try not to let him pick up on it. He will be listening to the tone of your voice as well as observing your physical reactions. They are very perceptive, as you know. At his age, I think you only need to let him know he's going in to have it removed because it's small right now, so it will be easy to remove; if ya'll wait until he's older it will be bigger. Honestly answer his questions, on his level, but don't offer info he doesn't ask about. He may ask if it'll hurt. My answer would be no, it won't hurt when they remove it, because you will be sleeping and you won't even know they are doing it. When you wake up, it might hurt a little, but if it does, we'll give you some medicine and it'll be fine. Reassure him, and yourself, that you love him and wouldn't allow anyone to do anything to him that is harmful.
Best of luck, and just KNOW it will all be fine. (-: