J.K.
Hi N.-
Regarding your concern on age, I became pregnant for the first time right after my 40th birthday, and just delivered my second child two weeks ago- just a couple weeks shy of my 42nd b-day.
As the other posters mentioned, do what's right for your family because it's what you really want. I'm sure your daughter will be fine as an only child or adjust well if you decide to have another.
Good luck!