I Want To Start A Family With An Older Woman

I am 22 and she is 42. I met her while I was in college where she worked at as a school counselor. We recently got married a couple months ago and are happily living together. She has 2 kids from her past marriage, a 14 year old girl and an 11 year old boy, which makes me their new step-dad. I like spending time with her kids, but I really want a family of my own, and I love my wife so much, she is the most amazing person I have ever met.  

So about 2 weeks ago, she told me she was pregnant  with our first child. I was ecstatic but hoped this wouldn't be our only child together. I told her that I dreamed of having at least 3 kids with her and she said she was up for it. She said that she also wished of having a big family but was uncertain due to her age. I told her it was possible because she was only 42 and we expected to have a child every two years so by the time we would have our 3rd child, she would be 46. We seem pretty optimistic, but what do you guys think?