I have been raised in a cat household, and I have 6 indoor-only myself, so it is imbred & stamped into my brain to just watch out for cats when I leave. When others leave my house (neighbor kids, my own daughter, etc.), I make it a point to drive it into their brains to "watch for the cats".
Mine don't want to go out, don't seem very interested; however, on pretty Spring days when there are squirrels & birds all over the front yard & on the deck, I betcha one of the boy cats would want to run out. So anyway, I always make sure the screen door is locked, when I exit, I exit backwards and I do the shooing thing (yes, I am paranoid), and I double & triple check to make sure no cats are near when a door is being opened.
Re: the nightlight --- I have a nightlight near each of the litter box areas in my house. I have 3 boxes in the basement, it's pitch-black down there; so there's a nightlight near the boxes. Also there's a nightlight in the laundry room (no window) and in the 4th bedroom. 4 of my 6 cats are older and Snickers eyes are really cloudy, you can tell he just can't judge stuff when he jumps --- so to make pottying easier for them, I have nightlights in each litter box area and also, I have some lidded boxes and some un-lidded. For better site & comfy pottying.