We have a number of Heinlein's science fiction "juveniles" on our list already.
I recently read (or re-read) some we haven't covered before to see whether they should be added: Between Planets, The Rolling Stones, and Starman Jones.
Between Planets: A boy in school on Earth gets caught up in interplanetary war and conspiracy. Allusions to torture, suicide, and violent combat.
Starman Jones: Boy runs away from bad (unsavory) step-parents, fraudulently get aboard spaceship (he confesses and is sorry later, though the consequences are minor), has adventures (creepy aliens) and rises to his destiny. (Classic fairy tale structure.) Probably the best story of the three.
The Rolling Stones: The extended Stone family leaves the comfort of the Moon for adventures aboard their own spaceship.
I wouldn't put any of these in the great category, though kids may find them more gripping.
The offensive stuff in these is mostly fairly subtle, brief, and allusional: a passing reference to "dancing girls" or descriptions of guerilla warfare with implied brutality. Tame by today's standards, but still may be not the tone you want.
There's some proto-feminism in The Rolling Stones, but the women still do the cooking.
I'm not inclined to recommend any of these at the moment. I should re-read the Heinleins we have listed now to see how they compare. (His Red Planet was one of my own favorites as a child.)