This doesn't make a lot of sense. Air has moisture, sure, but it doesn't deposit moisture on plastic surfaces, particularly hydrophobic surfaces. If you have humid air and you enclose the humid air within a sealed plastic bag, sure the trapped air will remain humid (for a time - eventually it will pass through the plastic, but this will be slow).
Even beyond that humidity won't pose a serious problem for DVDs. They are made from polycarbonate, which isn't a water impermeable as LDPE but it also isn't going to hydrolyze or anything in damp air. At worst, leave them in a dry place for several hours and they should be fine. If you are really concerned, store them with a good desiccant.