Hi, Elizabeth!
7-11 seems pretty broad to me. In the US, most kids turn 7 in 1st grade and are 11 starting 6th grade. That's a huge difference developmentally and in reading ability. You might want to narrow it down a bit.
Writing Irresistible Kidlit by Mary Kole and Second Sight by Cheryl Klein have been helpful to me. (The Magic Words, an updated version of the Klein book, is coming out soon.) I know you asked specifically for craft books, but reading lots and lots of other books written for the age you're writing for is also very valuable.
Hope that helps!