If you're in the USA, and you're male, don't do it. In the US, she can leave you at any time and by default get the kids, house, child support, and alimony. For a variety of reasons, the deck is obscenely stacked against you.

Regarding the kids, you have no idea how much you'll love your kids when you have them. But if she decides to go, she won't care one bit about that.

And I know what you're thinking. You're thinking, "Ah, but you don't know her. She's different. She'd never do that." I'll tell you what: people change -- in unexpected ways. Especially after the kids come.

Do some research. Google for "dads", "divorce", "custody", etc.