You need to be sure of where the mould is coming from. If it is just from the humidifier then you should be fine just doing as you are doing (if you have a steam cleaner go over the mold on the matress with it and then air it in the sun - it will also kill any bedbugs ). But if the mould actually exists because of another reason, unless you deal with that reason, then the mould is going to be a reoccuring problem. You can get special anti-mould stuff to put on the wals etc before you repaint.