Most of the trouble with night lighting is not the light itself. It is the gap between where the light turns on and where he actually steps. The job goes well when you treat it as a short project with a clear order: walk the route, pick the light, mount it, and test it the way he will really use it.
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Walk the route in the dark
Some evening after dinner, turn off every light and walk the path from his bed to the bathroom and from his bed to the kitchen. Use a flashlight only if you need it to stay steady. Count the steps, note the rugs, the door swing, the cords, and the place where the hall turns. Notice where your hand naturally reaches for a wall. Those are the spots that need light, and they are not always where you would guess in daylight.
Choose the light by where it has to start
Motion-sensor lights work well in hallways because they turn on as someone enters the path. Lights that stay on from dusk to dawn are simpler to live with if he gets up at odd hours and does not want to hunt for a switch. Low, warm light is easier on the eyes than a bright white bulb in a dark room. Avoid lights that point straight into the bed or the bathroom mirror, since glare at night is disorienting for anyone.
Plug-in, battery, or wired
Plug-in lights are the simplest route if an outlet sits near the path. Battery lights are easy to stick on, but they need checking and changing, and that becomes one more task on his list. Wired lights set into a wall switch or ceiling are a permanent improvement, but they involve electrical work. If you are not sure how the wiring runs in his house, stop there and ask a licensed electrician to look before anyone cuts into a wall.
Mount it low and aim it with care
Set the sensor low on the wall where the light falls across the floor, not across his eyes from the bed. Check the sensor's range before you settle on a spot, and aim it so it sees the walkway without picking up his bed or the television. Set the time the light stays on long enough for a slow walk, since a light that clicks off halfway down the hall defeats the purpose.
Test it the way he will use it
Walk the route three times in the dark, once at a normal pace and once slowly. Check that the light comes on before the first step, that it stays on through the turn, and that it does not switch off while you are standing still at the bathroom door. Leave the bathroom door open a crack for the first week so the light there is not competing with a dark room. Ask Dad to walk it once himself and tell you what he sees. He knows his own steps better than you do.
When to stop and call for help
If the wiring needs to run through walls, if an outlet is loose or warm, or if the sensor will not sit square without a new box, stop and get a licensed electrician. Mention to the electrician exactly what you want the light to do and where he walks, so the job is built around his route and not just the nearest outlet.