DVD use

[FlyMeToDunoon]

Do I lock them away and they can only be put on or taken out by Me, DP or Big Sister?
Or do I train DD3 whos is 2.9yrs to do this properly and hope that she doesn't trash anymore?

Your DD3 is trashing them?
Probably easiest to lock them away until she's old enough to understand how fragile they are.

Oh yeah she gets the cupboard open and chucks them on the floor in their boxes then tries to put one on or comes to me with a box and drops it disgorging contents onto floor etc....
Door locks here we come!

copy them and hide the originals.

Good thinking but slightly too techy for me.