You are getting some great input here. Someone mentioned getting advice from strangers, but somehow, I feel we've talked enough on the board and shared trip reports, that I don't feel we are strangers. I think I understand your philosophy on adventure, to some extent. That said, you won't be sorry if you push the envelope. As said earlier, even the long road days hold value.
If you feel you will not have a chance for a longer window (which I know you do), then do it. However, if you believe you could string together more time, another year, before the kids are raised, then I would go to the Black Hills and stop there. A more relaxed pace, and an awesome experience.
I'm thankful we saw all we did this past summer, but we had the time to do it without pressure. I'll be honest...Yellowstone would have been a let down for me if I had sacrificed too many other things for it. Yes, it is great, but it doesn't make my top 5 parks. In fact, the Black Hills and Badlands areas may rank higher in my opinion. Yellowstone may not even be a repeat park for me.
