That's clearly not what you said the first time Gappa, but sure, okay.
Godzilla's flying sequence was put in at the last minute to off set the grim tone of the film. Essentially, it was included for the kiddies and nothing more. Don't get me wrong, I'm not defending the scene (it takes you out of the moment every time you see it), but honestly, after 23 years of watching this film, I can just look at it and laugh. It literally only lasts a couple of seconds.
The boy is a supporting character in the film, and is hardly as cringe worthy as he is in MEGALON (I actually don't know the actors name, but it is the same kid). Seriously, when compared to the children from the Showa Gamera films, he's Oscar worthy in comparison.
I've never heard the word "goofy" to describe the soundtrack...unless you're referring to Godzilla's theme. Which, again, is all anyone ever references. If it just doesn't work for you, then that's fine. However that doesn't make it "bad" or "childish".
The animation sequences were definitely random, but it was just the way that Banno choose to keep the films narrative going. It was simply an artistic choice. The entire film was an "avant-garde" approach to film making in the first place, and it's important to realize that when trying to shit all over it simply for being different from the film's that surround it.