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.