Based on your size, stature, the fact that you carry a 25-lb baby all day, and you made it through a challenging 6-minute tabata...I'd say 25 lbs sounds perfect for you.
I'd also just add: don't over do it at first, and the instant you feel the "wrong" kind of pain...stop! Avoiding injury is crucial.
And as far as it being lady-like goes...it's all about the results. I'm amazed at how well women seem to do on crossfit-type regimens. My wife started off totally out of shape and thought crossfit was CRAZY. Now, she regularly out-does me in our workouts.