Concrete needs to be bound to the old concrete tied into the existing slab with rebar or some other fastening system. Think it will just crack again in those old crack lines.
This is the slabs weakest link and it will only probably crack in the new cement if placed on top of the old.
Would suggest to use furring strips and levelor boards to make the slab even and just put 3/4 inch ply wood flooring down This would be level and would be on top of the old slab and would be cheaper for you.
If the concrete is the choice, then consider removing the old and laying down more that is thicker and stronger and rebar enforced.