Our humidifier is connected to the furnace so when it kicks on it puts some moisture out with it. I don't think a portable one would hurt at all as long as it was up and out of their way. Be careful about keeping the door shut and the humidity level...my husband used one when he was sick a few years ago and insisted on turning it up on high
Well, when we woke up we had heavy fog in the bedroom and I almost espected to hear the fog horn and see a freighter pass by! LOL!