You seem to have a good melody, but I would consider less block writing, moving in blocks becomes really monotonous to the audience and they may get bored. Try having a counter-melody or something else to go along with the melody, instead of just block chords.
Maybe try having the opening as a brass fanfare style thing with percussion and then having the woodwinds come in later with something else.
Also, in regards to instrumentation, are you going to add oboes, bassoons, other low woodwinds, maybe a double bass and also extra percussion.
P.S. On a personal note, I usually really hate doubling saxes and horns, I found that it brings out the worst qualities of both instruments. Just being picky with this one though.
Aaron.