This is an excellent and entertaining video about Fibonacci numbers and the golden ratio.
https://www.goodreads.com/book/show/285503
I will probably have the kids copy passages into their journals. The amount of text per page is not too much to be overwhelming. Previously, we had been copying from 365 Days of Precepts by RJ Palacio every day for 2 years, and that book binding is completely ruined. The book exists in two halves now. Time for a change!