"Jazz" and "Orchestra" music are diabolically opposed musical forms. If you're looking for something easy to digest, I suggest big band, Ellington, Basie, Holliday, etc. For "orchestra" type stuff, I'd be looking more to the wind ensemble side, than the full on symphony orchestra music. Less strings, more horns, more drums. Aaron Copeland, Sousa, Owen Ried. Copeland is easy to find, Ried's La Fiesta Mexicana should blow just about anyone that's into complex prog/metal/math rock.
ANYTHING, and I mean ANYTHING from the Gil Evans era Miles Davis or Coltrane will get you hooked. From there, you can move to some the faster hard bop stuff.
If you can do a little more experimental/modern type stuff Weather Report's Heavy Weather, 8:30, and Night Passage. Chick Corea and Herbie Hancock aren't too far behind.
I could go on, but I'm trying to stick to stuff that isn't too difficult to listen to, and take very little "ear adjustment."