None. I'm not having children. I've made a promise to myself, and even if it comes between not having children and losing the person I love, I'm still not having children.
A few reasons, number 1, I'd be a terrible father. I'm a very selfish person, and I couldn't handle children. They'd end up growing up quite mentally fucked.
Number 2, I don't like children. They annoy the shit out of me. I can't be in a room with anyone under 12, or I have to leave.
Number 3, the world is fucked. Seriously, we're all going to die, and quite quickly too. Probably not in our lifetime, but certainly soon. I wouldn't want my children or my childrens children to go through that kind of pain.
Number 4, which kind of contradicts number 3, is that the only way we can save this planet is if a lot of us don't have children. Having children is one of the worst things you can do to the environment, overpopulation is killing the planet.
So there, that's my reasons.
I think it is immoral to have more than 2 kids, given how bad everything is. I wouldn't restrict it, and you're welcome to it if you really want to, but make sure you consider the ramifications of it before you have them.