Hi Bill,
Yessir, a room humidifier is perfect for what you want. FWIW, my guitars have been on the wall for maybe two decades now and between a wall-mounted hygrometer and the humidifier, they've all been perfectly happy. And just as you, I found that keeping them at arm's reach is the
best way to ensure they get lots of play ...soooo much better and worth the minor hassle of checking RH and filling the humidifier on occasion. A couple of points you'll need to remember:
- keep that door closed as much as you can to maintain consistent conditions and avoid big swings in RH.
- I keep the humidifier maybe 15' away from the closest guitar ...hopefully to ensure that the moist air flowing from it gets diffused into the room and
not blow directly or too closely onto any guitar.
- I keep the hygrometer on the same wall as the guitars are mounted.
Hope that helps you.

Edward