I think you're over-thinking this. It's not just a cliche that every story has been told already - it's the truth. There was a thing on NPR yesterday on that very subject, having to do with the pulp novels of the early 20th Century.
Certainly any number of big name authors have done the same thing. Jurassic Park is basically Lost World, just updated. No one complained.
Read the series, see the differences, and then go ahead with what you have. It's yours, it'll be different.
And I promise to stop reading your mind when looking for new ideas.
Write it anyway. The idea you have now may not be the executed idea that is your finished project anyway.
Even people who outline talk about how they veer off into the sunset from what they originally thought the story was going to be.
Until it's done, I would not worry. Write, write like the wind. You are freeeeee!!!!!!
This. Word for word, this.