All of the neighborhoods you've listed there are solid choices for a couple first moving to Baltimore. If you want grander rowhouses with more architectural detail, have a look at greater Charles Village (including Abell and Oakenshawe), Mt Vernon, or Bolton Hill. Those will probably be your best bets for good architecture + walkable + decent transit + diversity. I would also tentatively recommend Union Square - you can get huge Italianate rowhouses for not much money, the community association there is top-notch, and your commute to UMB would be a fifteen-minute walk down Lombard St - but the neighborhoods to the south and west are legitimately rough and I don't know what your tolerance for sketch is.

For what it's worth, I live in Bolton Hill and see a good number of kids of all ages around - from babies to "Congrats, grad!" signs in windows. It's more residential than Mt Vernon and Charles Village while still being within a 15-minute walk of most of Mt Vernon. I love it here and (assuming I can ever afford one of the massive houses) can easily see myself here for a long time.

edit: speling