I have been here in every season of Las Vegas and I just love this area of Red Rock! First off, it is in the free section of the park so it isn't as crowded as the paid area and you don't feel like you need to get your money's worth....
Secondly, you can reach the "red rocks" pretty quickly, which is great for kids. They love to climb all over the beautiful rocks. My kids have gotten older, but when they were young, the distance was really important and these areas fit the bill perfectly.
There are wonderful big and easy rocks to climb right at the beginning of many trails, so you can reach those quickly and look at the beautiful view which eating a snack or picnic lunch and letting the kids play.
You can also continue up the trails to much more challenging terrain.
In the early spring, you will often come across pools of water, which are fun to skip rocks and look for wild life.
During a few trips, we have seen wild Burros here. The most amazing thing is how they blend into the landscape so well, that you almost have to be careful not to accidentally happen upon them!
My favorite times of year for these trails are early spring or late fall.