The south and north rim trails follow the rim of whetstone gulf meeting on the western end of the gulf. Each trail is close to the same length giving a combined 5.4 miles to run both trails. Often times you're close to a drop off so keep that in mind with kids and or slippery conditions.
You have to pay to enter the park with a vehicle but on the other hand the trail is well maintained. It is an intermediate level run though once you've reached half way it is down hill most of the way. The trail is clearly marked and there are some amazing views!