Am I capable of writing the Talking Cake remake?

I've thought about it lately and I fear that because the changes I made to the book will be too mature and dark for me. Here are some hints to what I mean by dark changes:
1. In the new beginning, Carlisa and Will are said to had an affair. In Nohavia it is illegal to date a witch. When Trevor(Will's 12 year old brother at the time) sees the two together Carlisa attempts to get rid of him. Sure it sounds not that dark. Right? Did I mention that Will kinda set Carlisa up to attempting to kill Trevor and eventually killing Will's sister Hannah. Will somehow finds out about Carlisa's plan to kill Trevor but unfortunately sees Carlisa "kill" Trevor. In a panic Will escapes with Carlisa. Hannah finds Trevor, barely alive, and the two escape. After Hannah gets Trevor out of the city, she is killed by Carlisa.
Now Will believes that Trevor is dead and doesn't learn that he is alive till the end of the book. Claire keeps Trevor's survival a secret from Will because Trevor still hasn't forgiven Will for abandoning him.
My only worry about writing it is that this idea is soo mature and dark that I wouldn't be good writing it(description wise). If you guys have any tips on writing this book, please tell me. Have a great summer!
-AM