I would agree about putting a lock on the closet. 2 year olds can get into stuff they shouldn't. Putting stuff up high doesn't always work. We caught our grand niece at age 3 pulling out drawers in kitchen cabinets to make a "ladder."
As to shelves, I like the Closet Maid system. The house we just moved into had some wire shelves. I needed more in a walk-in closet for stuff like folded shirts, sweaters, shoes, etc. Get a small bolt cutter to cut the shelves to the proper length. Be generous with mounting hardware, braces, etc. I got all my stuff at Lowes, though Home Depot should carry the stuff as well. My local hardware store also had some stuff. Plan carefully so that you get all the right stuff, and save some trips.