Ehy @ezzy, another nice one.
I've watched this one briefly after it came out, and I have to say I agree with most of what you've said. There was something in the movie that didn't convince me as much as the first one, I can't really point my finger on it though. I guess that those plot elements you hinted about might be the culprit, but maybe it was just a generic vibe, a lack of originality if you will: if I single out every scene one by one I find them amusing and sometimes even outright brilliant, but the movie as a whole didn't work for me as much as I'd hoped. Then again, as you point out yourself, the intended target of the movie aren't adults, so I'm happy I had fun watching it. I liked the visuals too, but I noticed a difference between scenes inside the ocean and scenes set elsewhere: the former looked a little poor, detail-wise.

Side note: I'll keep reading your reviews, if only to read some of the comments under them. Some of them (if you're reading this, chances are your comments are not those I'm referring to) are so amazingly out of place that they become automatically a work of art.