This is not a post to say, "Do whatever you want." Because you will anyway. Good.
This is a post to say:
Don't find out. Leave baby's gender a mystery until you meet him or her. It may seem like an eternity to wait now, but you have the rest of your baby's precious life to know all about him or her. Gender is a scapegoat characteristic, the only biological thing about your baby that you can pin personality traits on. It's like a cheat sheet.
If baby's a girl, she'll be:
(see, you're already thinking sweet, beautiful, lovely)
If baby's a boy, he'll be:
(cue thinking strong, handsome, funny)
And those are just where you start. But the thing about babies, and people in general, is that you can't know these things yet. You can't know what your baby's personality will be until you meet him or her and your wonderful baby reveals all these things to you in the course of his or her life.
So maybe finding out the gender will make you feel more in control, like you can plan your baby's personality, but really, you can't. It's best to let go of that illusion now. Welcome your baby as a mystery to be unraveled as you get to know each other.
I'm sure knowing the gender doesn't take any of the wonder out of a birth experience. It's such an amazing thing that really nothing can diminish. But for me, seeing my little girl's tiny lady parts was better than hearing from an ultrasound tech, "It's a girl." (My husband was supposed to announce the gender, but he was too in awe to do it straight away, so I saw before I heard those words.)
And for your second child, people say that knowing the sex makes it easier to plan. Life is different when you are already parents. I say this now, but I do not want to know with our next children. I want to meet them when I meet them, in all their red, gooey, screaming glory.
Your babies' lives are going to go too fast as it is. Don't rush it before they're even born. Think about it.