You may not want to bring young children here...
First off, the Fremont Street Experience is pretty impressive, if not even jaw-dropping. The light show is properly psychedelic and not to be missed if you ever visit Las Vegas. Four or five stars for that.
However ... there are lots of people (women and men) standing around wearing very little in the way of clothing, and you can get your picture taken with them - for a price. Don't ask me how much, because I don't know. The guys with Spiderman, Incredible Hulk, Iron Man and Captain America costumes are kid-friendly, at least. There is a jazz sax man who plays soprano, alto and tenor sax, and he is pretty good. And the contortionist is worth watching, anyway.
You will also find lots of kiosks where you can buy tee-shirts and all manner of interesting things.
But, overall, Fremont Street should be rated PG-13, if not R.
And the postcards of "Sin City" invariably show some voluptuous chick, but maybe they should show some fat slob gorging himself at a buffet. That's a sin, too.