Well, Disney's Vero Beach resort (which is actually in Wabasso, a bit north of Vero itself) is 110 miles from WDW. I seem to recall the exit off of I95 for VB was perhaps 25 miles from Fort Pierce. You can get from WDW to Ft Pierce more directly on Florida's Turnpike, so I would guess the net distance to be 125-130 miles. It's a nice easy drive on the Turnpike too.
I hope this helps.