I haven't seen the movie, and of course in the book he's their child by birth (I heard one justification for this was that it's not "realistic" for a family to give birth to a mouse -- which makes no sense, because of course adopting a talking, car driving mouse is also unrealistic).
Anyway, as I understand it, the two criminals essentially
Giving away your own child to a stranger who shows up at your doorstep, is not a "mistake" whether or not you know they're criminals. It's a really really bad idea. How were they to know they were bad guys? If I showed up on your doorstep would you just assume I was a good guy and let me take your child and walk away?
It's a children's movie. These mice show up claiming to be Sturat's real family who were tricked into giving him up. They pretend to be earnest people who really want him back and have been searching for years. Teh human family belives them wholeheartedly, and do what they believe to be the right thing by returning a stolen child. It is not they think he is not good enough, not right for thier family. It is hard for them, but they do waht they think is the morally right thing to do.
The implication in giving their child away (even if they thought they were giving him "back") is that adoption is not forever, that the bonds are less strong, and that they can be broken. The implication that the parents thought he might be better off in another family, is that the parents were questioning adoption and that they felt like they'd made a mistake.
NO, again they thought that this child was STOLEN form his real family.
My child's adoption is forever. He belongs in my family just as much as anyone else's child. My family is as true and real as anyone else's. I have never and will never consider giving him "away" or "back", regardless of whether it's too a "good guy" or a "bad guy".
What is you found out your child had been a kidnap victim? That would muddy the waters a bit. He would be no less a real parto f your family, but alos a real part of the family he was stolen form. Taht is how I see the situation in the movie
That isn't to say I would never watch the movie, or allow him to. When it came out in theaters, he was too young to pick it apart an use it as an opportunity to explore and reinforce our family's values. Now at 10 he is old enough to do that but haven't asked to see it. I do know that even now, at 10, I wouldn't want him watching it without me there to help him talk through and process it. If the OP is trying hard not to offend anyone with this choice of movies, this would not be the right one, as you never know who has an adopted loved one.