Just saw it this afternoon. Took itself less seriously than the other "monsterverse" movies, and I think was the better for it. There were some good surprises, but also some surprising level of gore. I'm not really sure this one is OK for kids under 10 or 12? The way mini Kong gets treated was rough to watch. BTW, I thought running Godzilla looked stupid in the trailers, but I actually thought it worked in the movie, and the moment Kong and Godzilla team up is pretty fun! Edit: one more thing is that most of the human characters were pretty likable. It's just a monster that's the jerk. I think that was a plus.
Take my opinion with a grain of salt, but I think it's worth considering. My kid is 20, so it's been a long time since I've had to think about this stuff but here are the things that made me think this is for an older audience. Spoiler Kong rips a giant dog/hyena in half over his head, and the green guts basically cover him in gore. Kong is bit on the finger and attacked by mini kong, but then grabs him and uses him as a club to hit other giant gorillas. (If this has been "using enemy as club" but between equals, maybe not so bad, but here it's using a child as a blunt weapon.) Kong killing other gorillas by throwing them off cliffs, and the camera watching the gorilla scream in terror. Dan Stevens' character's taste in music