A cool mist humidifier is what you want to sooth irritated airways.
Vaporizers heat water into steam and they can burn or scald children who are naturally curious and active.
It’s unclear whether adding anything like Vic’s to the humidifier helps or harms. One study showed that these types of products causes airway tissue to swell; another thought it might help.
The most important thing to remember is to clean your humidifier so it doesn’t spread mold or bacteria.