When I worked in a frame shop and we had
to ship framed art, we never shipped with 
glass, only plexi.  A presentation in a frame
for the cel is nice, and if the person is 
purchasing the cel including the frame, I think
it would be worth it to have the glass 
replaced with plexi temporarily.  Make sure
you include a note to the person to get it
replaced with UV glass. :)

Jen