Yeesh. I leave for a couple months and the collective I.Q. here at THR drops.
If you are using a semiautomatic firearm for any kind of serious work, carry a spare magazine. Those of you who don't understand this have obviously not shot enough. Mags will fail, and at the most inopportune times. Five or fifty round capacity, carry a spare.
Kudos to the O.P. for thinking about this prior to an "event" at three in the morning. Rasberries to the "get a Glock with thirty round mag" crowd, who miss the point.
Personally, I have a small fanny-pack type affair that holds magazine, light and phone. Plan A, however, is an AR at the top of the stairs. Yes, it sports a light and I have a spare mag for it, as well. All four of us sleep upstairs and a bed check can be done in about five seconds to verify everyone is up here. Then I post at the top of the stairs with the rifle. Wife has the kids and shotgun at the opposite end of the hall (behind me).