My [48M] wife [34F] of 3 years has decided she wants kids. I'm done raising kids. Time to move on?

I already have three kids from my first marriage who range in age from 19 - 14. My oldest is in college, and come August I'll have a second in college - leaving only my youngest at home.
I am very content with this situation. I loved raising my kids, but I certainly have been enjoying them being more independent. The idea of starting over at this point in my life is not appealing to me at all. I can't imagine having a baby to take care of at my age and especially now that I'm getting used to again having some freedom and a personal life again.
When I first was dating my now wife, I told her when the topic of kids came up that I was not looking for a partner to have more kids with since I had three and they would be leaving the house soon. The idea of having a teenager in my 60s did not appeal to me at all. She said at that time that she was fine with this because she had never had a particularly strong urge to mother children, although she did like them, and wanted to spend most of her attention on her career.
Now she has changed her mind leaving me in a position where I feel like I may have to end our relationship for the benefit of both of us.
My wife has explained that although she didn't initially want kids, after getting to know my kids better and seeing our relationship and bond and also seeing what being a father had meant to me and how happy it had mad me, she now without a doubt wants to be a mother.
I can understand her position, but that doesn't mean the right choice for me is to have another child.
She asked me to consider it and to discuss it with her, and I have and will continue to do that for now. However, I can't help but remember every time we discuss this that I'll be 49 later this year, which means that even if she got pregnant in the near future I will be almost 70 years old by the time that child leaves the house. I may not even be alive! Not only that, what kind of childhood can I give to our child when I am a 50 and 60-year-old man?
I think that it simply comes down to me being too old and her needing to find someone else. She says that she doesn't want to consider divorce or finding someone else because she wants me to be the baby's father, but I think I am too old. I worried that if I am not the one to end things she will stay with me even at the expense of her happiness. I don't think she would resent me later, but I do think she would have regrets. I don't want her to look back on her life someday and wish she had children since this is something she clearly wants.
Two questions. 1) Is ending things the right call? 2) If so, what is the kindness way I can do that?
tldr: My wife has changed her mind about wanting kids after getting to know my three from a prior marriage and seeing me parent them. I think I am too old and enjoy my newfound freedom to start over, but I am afraid that she will stay with me and later regret it if I don't end things. Break up?


Source.