I know you said your question is for people with more than one child but, I just want to tell you why I choose to have one.
The financial thing, for me, isn't necessarily overwhelming. You WILL naturally find a way to delgate funds. For, however, I don't want to short change my son when it comes to education. I want him to have a great educational environment where he's nurtured rather then just another social securtiy number. This of course takes $$. If I were to have another I'd have to put them both in public. Nothing is wrong with public school. I went to public schools all my life and have a great career now. I just wish to go private for my child.
Also, I want to be able to be a huge help, financially, when he needs his first car, apartment, wedding, business endeavors, etc.
Is it worth it to have more than one. OF COURSE!! Children are amazing gifts. I daydream of a little girl here and there. But, I was an only child and my parents were able to revolve their lives around me and only me, which had a huge deal to do with where I am today.
What ever you decide is the absolute right thing. I think if you've gone this far considering it, then you should in fact do it. Again, nothing will be overwhelming, it will all be beautiful. I'm just putting out there what my own thought pattern is when it comes to my decision of sticking to one.
If I were a mutli-millionaire I'd surely have 3 more. LOL.