Can't keep anything clean

DVD HELP! My kids won't put the DVDs back after they watch a show and I just put them away and well were missing one. arrgg. I do try to get them to put them away after but they never do. Then when they pick one up it has finger prints all over. When they leave them out, Sariah now will pick them up and well everything she picks up goes in the mouth. So now we have scratched DVDs. I've tried to put the DVDs in a cabinet with a baby proof thing on, Conner figured them out pretty fast. He can even open the baby proof door knobs, that kid figures stuff like that out so fast. Kate doesn't know how to open the door yet.
If you have any ideas on how to keep these things safe that would be great but I guess nothing last forever. Oh Well.