The only problem is Chomper isn't going to be sticking around the valley by the time he and Littlefoot are of age. He'd either die of hunger long before that, or start eating dinosaur meat, and I don't see how he could really stay in the Great Valley and do that. He'd have to force himself to leave at some point, if he wanted to make sure he couldn't hurt his friends.
Just something to consider.
that is my greatest problem I had, but I had a plan for that. Chomper was thin, but he ate. He just ate fish and other things that were non-dinos. He even eats Tickle Fuzzies. And no, he didn't live in the Great Valley all that time. He was back home with his parents after Red Claw's defeat, though Red Claw survived. What he did in private, er, can be left unsaid (You can pretend that it was Yellow Bellies.
) It is known that he never said he ate leaf eaters. He came back after having to run from Red Claw again. As they trusted him before, they let him back in. (In fact, Littlefoot's constant vouching for him is kinda what led to the banishment. When you vouch for someone and things go south like that, you pay the price.)
As for why he ran, apart from being chased by Leaf Eaters, he was afraid that what happened to the Old One would happen to Littlefoot next.
I do have something else that Chomper can eat and that nobody would much mind if he did in the Great Valley, Egg Stealers. He can go out in the Mysterious Beyond and go them there too. Anyway, he has a mate to help him by movie's end.
Anyway, even if Chomper ate meat, the premise is that he never actually did the killing but others would for him. (He got his parents to do it perhaps, as he couldn't bring himself to do it.)
Though, on the flip side, that kinda messes with my part where he goes all nuts when getting leaf eater blood on him and nearly eats the Old One. (i.e. she didn't die from a bite in the end, but a stomach injury form his claws.)
True, it's not going to be fully believable if one looks closely enough, but, then again, we don't want them being so separate in the end, do we?
Also, my kicked out scenario would be where Littlefoot is about 2 or so weeks from his coming of age birthday. I mean, we can jail kids old enough now as adult offenders so it's not beyond the realm of believeability in that scenario.
Of course, if you must insist about Chomper, perhaps the Great Valley comes to accept what he is and concludes that, if he hunts in some place outside of the Great Valley where it's not one of them and they don't have to see it and don't have him tell them, they will be ok wiht it.
People turn a blind eye to things they might not like for the sake of friends. It's certainly believaable there.
Besides, after Littlefoot gets redemption and gets back in, he and the other members of the Gang of Five, and perhaps Ruby too, will be grownups and hence have some say. Perhaps they can use sway to uphold such a decision. (Note: Chomper would need to get redemption too, but the scenario would get them redemption together.)