For the ages of the kids, I’d recommend for westerns with John Wayne: Big Jake, the Cowboys. (Not John Wayne but good one: Dustin Hofman)Little Big Man
WWII: Something light but yet show some of the hardships:
Kelly’s Hero’s, The Dirty Dozen, The Great Escape
Maybe Stalag 17.
As a kid, my favorite WWII was Sands of Iwo Jima but thinking of kids today, the above are movies I think kids the ages you mentioned would like.
Would you like to come sleep on soft furs in my tent, Little Big Man. A Man Called Horse is good, too. Jeremiah Johnson.