Flying DJI drones is like riding a bike. Once you learn how to fly one, the next model is just as easy to fly. So there's no single model that's better simply because it's beginner-friendly.
It depends on what your son plans to do with the drone...
Litchi uses the DJI SDK to communicate with the drone, and control is handled through the remote controller. There shouldn't be any issues, but if you're unsure, it's always a good idea to check with DJI Support.