DH and I often did this at CS. He'd order an adult meal, I'd order a kids' meal, and we'd share our plates. Often, the kids' choices looked better than the adults' to me. I am also a snack-through-the-day person, so I was rarely hungry for a big meal. Disney charges a lot for food, but they do give you a lot too!
If I'm up at the counter ordering a kids' meal and an adult meal, the CM has no idea who I'm ordering for. I could have a whole table of kids sitting outside or one hungry DH! No one's ever said anything. TS might be different because they see your whole party.
PHXscuba