Yes, the 3-book series of Misty is just right for an 8 yr. old. Then BLack Beauty and Black Stallion and Henry’s other horse stories as well. My dd really enjoys her Album of Horses, too. For the younger ones, Big Black Horse; it is the authors own adaptation of his own book the Black Stallion. This one was my dd first horse book and she will not part with it at age 9 1/2!
Also, Dover has a wonderful collection of horse coloring books. Plus, they’re having a very good sale.
For movies, the new Black Beauty is excellent but it’s too dramatic for your younger ones. However, they could all enjoy the Elizabeth Taylor movie National Velvet from 1944; based on the book of the same title. You can probably find it at your library and if you have Netflix, get it there.
I am very happy for you and you choosing this path of living and learning; especially with as young as yours are. Your 8 yr. old will soon recuperate and come alive again!
HTH, Rachel