Hope this helps redone,i played clarinet,alto&tenor sax in high school,college,dance bands.Depending on your instrumentation and selection (orchestral,etc) of music,and sister's skill-can add some melody,bass,wind parts for her.A good source to study voicings would be to get some scores by alexander publishing similiar to what your church uses,get multiple parts-clarinet,sax,trumpets,t-bone-etc ,see common parts ,should give you an overall feel.Any local music store should have materials to help you get started.It may be at an elementary level,sounds like you just need a jump off point.Of course,little praying see what LORD's up to always a good place!