These may be a little young for him, I read them all when I was 8.
Heinlein juveniles,
Rocket Ship Galileo, 1947
Space Cadet, 1948
Red Planet, 1949
Farmer in the Sky, 1950
Between Planets, 1951
The Rolling Stones aka Space Family Stone, 1952
Starman Jones, 1953
The Star Beast, 1954
Tunnel in the Sky, 1955
Time for the Stars, 1956
Citizen of the Galaxy, 1957
Have Space Suit—Will Travel, 1958
Have you looked into Greek and Roman Mythology?
