When my HD rep asked where I was going to do prep work I told her it all happens on site just like any BBQ. She said, " I get it you buy the burgers, pork, sausages,ribs, chicken etc. from the butcher or cash and carry then season it on the grill as you cook ...right!?" I said yup thats exactly what we do. She checked of the box and went to the next part of the questioning. Now I know things are not the same over here but can you try something going that route?
The next part was transport and refigeration-
At the time I was using ice chest to transport my raw goods and that's not a problem with them, the only thing needed it a way to check and keep record of temps. I'l look and see if I stil have a PDF copy of the log sheets.
I don't mess much with coleslaw but it's easy enough to buy in if needed.