Do the 2 witnesses need to be present during the drafting process or know about the contents of the Will?

For the Will to be legally valid, it needs to be printed out (i.e. in hardcopy) and signed by the testator (your client) together with 2 witnesses.

The witness do not need to be present during the drafting process, in fact the witness does not even need to know the content of the Will itself. The primary purpose of the 2 witnesses is to witness the testator (your client) signing the Will (by signing of the Will as witnesses).