Great question!
A couple of considerations:
If you place the elements on the page but disable them, there's still a remote chance that the user could doctor the system and enable them using a javascriptlet.
If you do not show them at all, the overall functionality may be a bit confusing to the general user. "Shouldn't there be an edit button here?"
If you're going to either display and disable or display and verify the elements, I would definitely do server-side validation. Don't leave the validation in the hands of JavaScript; I think the reasons for this are obvious.
