The Randall Henderson Trail is an easy trail with little elevation gain suitable for the entire family. As a bonus, it starts at the Santa Rosa and San Jacinto Mountains National Monument Visitor Center, which has some nice exhibits.
The Henderson trail, while easy, does contain a number of common desert plants, including cholla cacti, barrel cacti, creosote, brittlebush and more. In fact, the annual Coachella Valley Wildflower Festival, held in March, offers free guided tours using the Henderson, which is when I walked it.
If you conquer the Henderson quickly and want more, there are several trails that connect up to the Henderson for further exploration.