I'll admit I didn't think this through properly.
I've done the same trip often before, just made the lunches before we leave, put them in cool box in the boot with ice blocks, leaving it in the car overnight.
However, it is currently unusually warm and (this is the bit I didn't think about) in the past we've left later on the Friday, after work.
I could stop and buy something ready made on Saturday morning but money, time etc.
What do you think? I'm not going to do anything stupid like prawns, but if I do safe foods (cheese?) will it be nice to eat by Saturday lunchtime?