You should try and break down programming concepts and ask lots of questions to see where their gaps in knowledge are.

Instead of doing all the coding yourself, leave it up to them by getting rid of some of what you build and hand it to them as isolated exercises. This will allow you to test their abilities incrementally and also give them a boost in motivation to see something working.

Teaching others how to code is another skill to build just like programming. You will learn through practice and get better at explaining abstract concepts with clarity after explaining things clumsily the first time. Just keep at it.