Hmm. I'd start with a lower note in the begining. (Refering to the first one *doesn't have tabit*)
Don't go too far off with the range, and keep in mind what you're trying to say with the music.
Keep the higher octave notes for a climax in the song. The rest should build up to it.
Also, being a trombone player, I know how difficult it is to reach some of the notes you have the tuba player. Seeing as the tuba is lower than the trombone, I can only ask that you make it a tad bit lower.
Fun song.