Kinda obvious I know but it sounds like he needs told, he need to do a quick check before leaving home each time.
Guns,
Ammo
In a range bag: Set him up with one if he doesn't have one.
Mags, Targets, Stapler (or stand for steel plates), Ear and Eye Pro, lube, basic field tool needed to work on guns, hand sanitizer, etc, etc...
Each persons range bag may differ some. My dad shoots Black powder only, so he is gonna have a buncha shit in that I'd not use.
One of my step sons has a few range bags, he shoots more and more often. The other son has a range box with a few things...