Hmmmmm well first I think it'd depend on how the kiddo handles scary things. It has your typical scary movie stuff - creepy faces, things that will make you jump, scary clowns, loud bangs, things flying, people being dragged, etc. I don't think it was overly scary but I think it would be scary for a 6 year old. If your kid is ok with knowing it's just a movie, it's not real, and the whole point of its creation was to scare you then I guess it'd be ok. (Still pretty scary for them but nothing extremely traumatizing.) I don't think it was any scarier than the original, just updated to fit in with the 21st century.
From what I remember there wasn't any overly adult scenes. There's a scene in the beginning that the parents start to get undressed to have sex but one of the kids walk in right as the dad unbuckled his pants and it ends. Lasts all of 3-5 minutes maybe? It's mostly just talking and husband is leaning over the wife and they're being all seductive.
There isn't a lot of gore, just slime/gook. Not a ton of suspense (but I knew what was going to happen since it's a remake). There's a pretty suspenseful scene in the middle but nothing bad happens.
Also, and I think they should've put a warning out for this, but I thought it was very flashy. Like it could cause health complications if someone is sensitive to light flashes.