Sushi Rice and Kids

I am going to apologize in advance for my truly novice questions. I have looked at some of your blogs and I am officially intimidated. I am just starting and have a lot to learn. My question is that I see so many bentos using molded rice as one of the main ingredients. My questions are: What is your sushi rice recipe (I've always made it adding just a little rice wine vinegar)? Are you using sushi rice for kids' bentos? And if so, what age, are they eating it, and how do you deal with heating it up (or do you) when other parts of the bento should remain cold? And what is your favorite mold? Thanks in advance!