I've done a few fashion shoots such as you describe. Sometimes they don't let you quite as close as you'd like to get. Other times you can get as close to the catwalk as you want to.
How close or how far are you going to be from the catwalk?
Any which way, I'd keep the 80-200 on one body and either the 19-35mm or the 24-105mm on the other body, depending on how close or how far you're going to be from the action.
Can you scout ahead and see?
That way you'll know whether or not you'd want to talk to the designer about getting closer, maybe.
The lighting in all probability will be completely unpredictable so you'll have to rely on a flash for every shot so that it washes out any colour casts you might get in your image.
Rear-sync will come in handy if you want to experiment and get a few interesting shots, as will the 'strobe' function.