Need help with some background

I've been working on this piece for a marching band for several weeks now. I don't have much done because every time I get anything written the people I'm writing for have to listen to it, in order to "point me in the right direction." So far I have a small intro with marimba and vibes, followed by a duet of an alto sax and trumpet. Then a big hit, brass, then woodwinds separate. Then a groove starts. I've got an okay brass groove, but I need some woodwinds besides alto sax to support this groove from all around. Trombones have the melody at this point and at the end of what is written is the trumpets coming in to remind you they are here to play. Well, what I need help with is the woodwind part starting at measure 21 if anyone could help, thanks.