Ohhh, I definitely recommend Galaxy of Fear books too! I read a couple of them when I was younger, and they were fun to read.
For the purposes you’re seeking though, they aren’t canon, meaning, they don’t tie directtly into the films or Disney’s new Star Wars canon. However, for as young as your son is, I don’t think it will matter to him. So long as he’s getting some Star Wars adventure stories within some cameos of characters like Darth Vader, he should be satisfied.
For your interest though, if seek new canon related stuff, there’s this Reddit post breaking down what Disney has put out so far.