You still need the Neodymium magnets - these circular ferrite probable dont have necessary force to work with HALL. But make a test.
I suggest use just for shield - in fact only the case of motor (or a piece of tube of ferrous material) is suitable to shield. But start without this, probable find that is not necessary.

DIY HALL assembly is very flexible - you just need do some experimentation. Just dont mix + and - wires. smile