I don't have any advice as to which breed is better but I can tell you what my experience has been with young children and a Yorkie. I have a 2 1/2 year old son and a 9 month old baby girl. My puppy is almost 14 weeks and we've had him since he was 8 weeks old. I purposely got one that was fairly sure to get a little bigger, in the 7-10 pound range, because of having young children. My son is very good with Max, they chase each other around and wrestle on the floor. Carson knows not to hit Max or throw things at him. Becca tends to grab Max's fur and doesn't yet know how to "pet" him but Max is very good with her, doesn't bite or jump on her. He visits with her for awhile but soon moves on as he gets tired of the fur grabbing and head bonking.
Potty training Max has been a little rough to start off with but this past week has been great. I was using the crate training, then I wasn't and now we're back to it. It's working out really well this time around. It's really nice because when things get a little out of control or I need a break, I can put Max in his crate and know that he's safe and not getting in to trouble around the house.
Good luck in your decision! You'll be happy whichever breed you choose!