For me, the question isn't so much "Have you become less ambitious about your career and personal goals since having kids?" and more like "How would your ambitions and goals be different if you DIDN'T have children?" since it's always overlapped for me. I've been a mom for all of my adult life - my son was born when I was 20 - and have pursued my career for most of that time as well, so the practicalities of family life have shaped everything.
When I became a parent, my son's father and I were both still full-time college students, and I had decided to major in accounting since I thought it would make me employable pretty much anywhere (good call, although I'll never truly love it). Knowing we would be a two-career family with a child from the get-go certainly steered me away from pursuing a path in public accounting after college (although in the last 20 years CPA firms have actually made a lot of progress in becoming family-friendly). Wanting work that wouldn't have to follow me home often, and an environment and schedule that were more flexible and responsive to family demands, have been major reasons why I've stayed in the nonprofit sector, and haven't pushed too far up the corporate ladder - I'm comfortably residing a couple of steps below senior management, and have fewer headaches.
I'm aware of what happens to me when I push myself too hard for too long, and it's not pretty, and since being a major player in my family's life matters more to me than any other arena, my ambitions on the personal side are scaled to that. After a certain point, "balance" becomes almost a physical need for me in order to function, and I wouldn't consider myself especially ambitious or driven most of the time. I'm inclined toward the smaller, reasonably achievable goals, and I do feel like that's a tendency influenced by parenthood - but I'm not sure how much MORE ambitious I'd be without kids in the equation, and I think it's probably too late to figure that out now.