Give him a big fat bonus at the end of the pay year.
Tell him of your intention to do this.
As for the second part of the question:
while not making him feel pressured to keep working late nights?
I would cushion the conversation with 'but remember that your bonus depends on the the whole year's performance - I really don't want you getting burned out', take a few days paid leave, and let's work on being more organised going forward'.
Ask him his recommendations on how you'd be better organised next time. That's going to make him feel valued.