Is there a fee to use an outside vendor - or trio in this case - for the ceremony? I know if you bring in a DJ or band there is a fee...but what about for a 30-45 minute time at the WP? Has anyone done this before?
I have never heard of an outside vendor fee for musicians, just the prohibition on non-Disney musicians at outdoor venues, which you don't have to worry about with the WP.
The fee for bands and DJs is to cover staging, lighting, etc. A trio is probably going to bring everything they need but the chairs (and who knows - maybe they bring chairs! )