This is something that you absolutely have to do when you visit Las Vegas!
A lot of people overlook this tourist attraction because it is not on the "new strip". It is actually where the strip began before it expanded to the south. It is an absolutely totally different vibe from the south strip which is where the major casinos are now.
The Fremont Street Experience is best seen on a Friday or Saturday night. That is when they have more of the street performers out but even on another night of the week you will still find an abundance of street performances.
If you track to the east end of the Fremont experience, there is a great little Thai restaurant and then a little east of that is what's called Container Park. Overall, a lot of great little non-chain restaurants to try.
It still has the largest LED screen overhead the walking area. There are also typically live bands and great small shopping kiosks.
My warning would be that it is not very kid friendly at night because there are a lot of mostly nude men and women that are 'performers'. I don't have children but if I did I really wouldn't want them exposed to that so I totally get why that would turn some people off.
But again, I still think this is something that you must see you before you leave Las Vegas!