Anything, once cured, should be non-toxic. However, anything that
cures can be cut through, chipped, etc. The whole point of using
mineral oil is that it does not cure, so you can't cut through it or
crack it or chip it - it just soaks into the wood and stays soft. I
haven't tried mixing mineral oil with paraffin, but it sounds good - if
thie mixture is thin enough (maybe applied warm?) for the wax to soak
into the wood, it should stay soft enough to avoid any cuts or chips.
But then again maple (or any good cutting-board wood) has small enough
pores that it shouldn't soak in very far anyway...
Andy