Hi Sherry!
I’m in a similar situation with the ensemble at church, and also with my own ensemble. I’m about at your experience level, so I know where you’re coming from. The single most valuable advice I can give you is to learn your chords. You can let the flautist and the violinist take the melody/harmony on most pieces, let the guitarist back up on chords, and throw in some runs and arpeggios to fill in and give that beautiful harp sound to your arrangements. This is how I worked out a lot of pieces and it always sounded good. Plus, by learning the chords you can make the music unique to your ensemble, instead of memorizing someone else’s arrangement.
Of course, this is a simple and easy method of working the music with an ensemble. You can always challenge yourself by learning a complete piece, and letting the violin & flute fill in by either playing the melody in a different octave or playing notes within the chords as back-up. Either way, have fun! I am excited for you
Just an additional thought: listen to CD’s of ensembles with the harp. Pamela Bruner has some nice ones out there that feature cello, oboe, violin, and pennywhistle, to name a few. It has always helped me to listen to how others arrange music, just to get a “big picture” feel, if you know what I mean.