Okay, just thought I'd give another update on our trip back.
I checked in right at the 24 hour mark and our party was fairly split up. The seats were 11F, 12E, 14C, 14D, and 14E (14 C is across the aisle from 14D). The 4-year old and her mom were 14D & E. The rest of us didn't mind being split up like that at all and again, nobody else seemed to have any problems on this flight -- at least that I could hear.
Had the 4-year old not been with her mom, however, that might have ended up being a problem. She was worn out at this point and had a bit of a hissy about being seated next to a strange man. She kept saying loudly, "Why are you making me sit by a MAN??" so her mom switched with her and she kept saying "Why are you making me sit here??" The guy said to her, "Well I'm not too thrilled sitting by you either."

I know it sounds really bad, but it was actually pretty amusing to everyone nearby. I offered to trade the guy with my aisle seat but he said he was happy with where he was, so no harm no foul, I guess.
As the plane started backing away from the gate, the little one announced very loudly that she had to poop, which horrified her poor mom and made people laugh even louder. Thankfully she settled down and was a joy the rest of the flight.
Now what makes me curious is, aren't the seats behind business class usually reserved for AirTran customers wanting to pay the $12 seat fee? I honestly didn't expect to be sitting so close to the front like that. I'm so happy we were, but it was a surprise.
Anyway, what I took from this experience was, if I'm traveling with adults, I'd definitely do it again. It's not a big deal to split us up. But traveling with a little one? No. I'd either do Southwest through the SW site, or AirTran through the AT site. It's not worth taking the chance of being separated from a young one, especially if you don't know how they'll react.