I totally agree about toddlers being kept away from the flock. Not a good mix in any situation.
That being said, my kids chores include collecting eggs and feeding the flock. I do morning chores, they do evening chores. My kids are 8, 12, and 14. I honestly think my 8-year old daughter is most likely to smack a roo for getting cocky of the three of them. I have told them the signs of aggression to look for and to never turn their back on the roosters.
I have thought of something in reading this thread...I am building a coop with breeding pens in it, and each pen will have 5-7 birds with one roo in each. I am thinking once they are more confined for the winter, I should probably take my daughter off the chore rotation or at least pair her up with her big brother or myself. I love my roos, but don't trust any. I have one NHR that already makes little attempts and I give him a little unexpected flight across the yard off the end of my foot. The kids know they are to watch him and don't even let him look at you for half a second.
I do think it is important to start teaching kids when they are young (I know toddlers are too young to understand) how to act and what to watch for around chickens.