Brad... whe I worked as a photo editor, I preferred 4x5 trannies to be sleeved, not mounted. You can either sleeve them individually, or in a sheet with four transparencies. Make sure you have small stickers with your name, etc. on the sleeves. You should have a delivery memo, and a xereox copy of each transparencey submitted. The delivery memo should stipulate that the photographs are for review... they should call if they want to use them. If you send originals, then they are liable. Industry standard (then) was $1500 to $2000 per slide if they are lost or damaged. State that on the delivery memo. Also state that they are due back on two (or three) weeks. If they still need them, you (or they) should call for an extension.
As Don says, sending a CD would probably work. We always got better reproduction from originals, but these days, that may have changed. You could certainly send a cd for review, and an original for reproduction, if they want. Make sure your cd is compatible with their system. If they can't open an electronic file, they'll never see it, and if the deadline it tight, well, someone else's pic will be selected.
Good luck!