We went to Ohana with our daughter when she was three, and she had a fabulous time. They have music and interactive dancing there (at least in the evenings, they did) and she loved that. She also liked to try all of the various meats and other dishes delivered to our table, but our server also offered her the option of getting one of several basic kids meal entrees to supplement her dinner. I believe they just get that delivered over from one of the other kitchens at the Poly.
I'm not 100% sure whether the alternate kids meal entree is something that is regularly offered or if it was a spur of the moment offering from our server, but we didn't inquire about getting her anything other than the food being delivered to the table, it was just spontaneously offered to us. I think they may do that because meat is sometimes a pretty hard sell to the preschool age group.
(She did choose to have some mac & cheese after the server offered her a couple of choices, but she mostly ate the regular Ohana fare, which we all liked when we went.)