Deleting All Items?

I am switching to a survival world soon and ALOT of my users have items they have got via Creative.
Rumors have spread of me deleting the items and now they're placing the items in ender chests and placing Diamond Blocks on the ground ....

I tried world editing the chests out, but it crashes >.<

 

I dont think there is a way, Possibly be a little tricky? Like this

Say this "Guys, Attention, The server is not going to become survival, We are staying creative!

After about a week, Change it to Survival without notice. People will be caught off guard.

This might not get rid of all the precious items, But it will get rid of some.

 

Delete the world entirely. Only way to be sure.

 

Alot of creations made, people would be very angry >.<

Sorry to bump, but I have until tomorrow to find out a way to do this.

EDIT by Moderator: merged posts, please use the edit button instead of double posting.

 

Don't you have backups of your server world??? If you don't, then you can just use the command: /invsee [playername] to take spawned items out of their inventory when they eventually do take them out.