Nahal David is the easiest hike in Ein Gedi. It's well maintained and not at all difficult, to the point where it's become a sort of family outing during the weekends and holidays. What's good about Nahal David is that a 20 minute walk offers you some pretty waterfalls and pools. On the other hand, the price of its success is that it is so busy it gives you the impression that its part of the artificial scenery of a theme park. If you are a true hiker, I recommend you keep walking once you arrive at the David falls. There's a steep, slope which is exposed to the sun, but during the climb you will find a refreshing pool and a spring, as well as some ruins.
Whether you choose the long or short option, Nahal David is a good opportunity to hike in an oasis during your trip to Israel.