I'd like to see the mothers be able to earn some tech points. Any real parent knows it is hard work!
I'd like to see some "bratty" behavior from the little ones. Throwing a tantrum, doesn't want to share etc... and then interaction from an adult ... scolding child, sending child to time out. The child could grab a collectable and not want to put it in the research hut until spoken to by an adult.
I'd like for the little ones to go to an adult or nursing mom if something scares them or they fall or someone hurts their feelings. Some more interaction with the mothers than just wandering around alone.
Maybe at least be able to hug an adult without the adult running away because "this villager is too young." That seems perverted!

I love the babysitting idea too!
I'd also like to see a father(s) stop what they are doing every once in awhile during the 2 years and show looking at baby. Checking on mother and child or something. He can go eat or get a drink, he can swing by!