Many, if not all, of the signature restaurants have a steak on their kids' menu. If you don't plan on dining at any signature restaurants, you could always order from the adult menu for your child.
You can find steak on the menu for kids at ......Le Cellier, Flying Fish ( beef skewers), Cali Grill (Oak Fired steak), Narcoosee's (filet mignon), Ohana (sirloin steak), Yachtsman Steakhouse (oak fired steak)....... those are the ones I could find. But you can see most all the menus on Allears.
We were just at Le Cellier last week and ordered a steak off the kids menu for my DD (8). We are on the dining plan, so we were to be charged an additional $2, but it never showed up on the bill.
Just wanted to add that you could also get steak at many of the buffet/ family style restaurants where there is not a separate kids menu. I know 'Ohana, Crystal Palace and Chef Mickey's all had some kind of steak when we were there. I am sure there are others.