Q: 2 questions...1 how do you permanently delete apps from devices/itunes/icloud 2.I have two children with ipods now whats the best way to keep there itunes apps and such seperate from mine?

It's not currently possible to permanently delete any items from your purchase, all you can do is hide them so that they are less visible (e.g. they won't appear in the Purchased tab for re-downloading) : hiding and unhiding.

If you share the same iTunes account then don't use automatic downloads otherwise their downloads will appear on your devices. If you sync to the same computer you may also want to make sure that the 'automatically install new apps' tickbox is unticked - that shows on the device's Apps tab when connected to your computer's iTunes, under the listbox of apps (where you select which apps to sync to a device).

There is also this page for multiple devices being used on the same computer : http://support.apple.com/kb/HT1495