Measurements of double‐spin asymmetries for single‐inclusive heavy flavor production and for heavy quark correlations are expected to provide valuable information about the spin structure of the nucleon, in particular, the elusive gluon polarization. We discuss progress towards a versatile parton‐level Monte‐Carlo code for the production and decay of heavy quarks in longitudinally polarized proton‐proton collisions at next‐to‐leading order accuracy of Quantum Chromodynamics (QCD). First phenomenological studies are presented for BNL‐RHIC.