My wife says NO for the kids.
Not sure how old your youngest is? We ended up hauling our 6 year old along to a showing last Friday. There was more ear-covering on the loud sounds during the previews, but he ended up being just fine with the movie.
Nothing really too scary for him, but I think he was a bit impatient during all the talking scenes (how dare they not have some superhero fighting at all times!!). He walked in an Iron Man fan, and walked out an Iron Man and Hulk fan.
The only real impact to the kid was a bit of hyperactivity after the movie as he felt the need to smash everything.