Well, it didn't turn out so bad after all.
The garden only hit 41°C today, and at the time these photos were taken (7pm) it was still sitting at 38°C. I imagined I'd be returning home to see pumpkin leaves drooped on the end of their stalks - and they had been at about 1pm - but the wife kindly broke from protocol and did a little gardening. By the time she finished watering everyone was feeling a bit less scorched - except her.
In fact, there seems to be little or no damage to any of the plants today - not that there's really much else other than pumpkin to speak of - And thankfully, it's looking like there'll be a few more of them yet.