Why did only the adults look tasty to the Yolkians? Shouldn't children be like veal for them? Or is it like fruit to them, and they need to age and ripen? (I freely admit to not seeing the movie in years, so I don't know if it is explained, I just don't remember if there is one)
Well, the adult humans were supposed to be sacrificed to the Yolkians' giant chicken god. No one was about to become lunch for a Yolkian. The kids, I think, were too small to be considered by the Yolkians as anything other than an insult to their god if used as a sacrifice, especially when there is a planet full of much larger humans within range of their fleet.