What useful tools do we have for teaching and studying the vocabulary? Is it only a notebook with word lists?

My son is 4.5 years old. I decided to teach him English. I teach young adults at a university. So what did I do? I found a book and tried to make him sit down and work with me.

Is it possible to save in our computer the flashcards that we have made? Otherwise, they can not be modified any more.