To assess the importance of coupling to electron-hole pair (ehp) excitations for molecular sticking, scattering, and diffusion dynamics at metal surfaces, simulations of the CO/Cu(100) system were performed using the "molecular dynamics with electronic frictions" method. Over a range of incident translational energies, energy losses to ehp excitations produce a moderate increase in sticking probability and account for 5%-10% of initial translational energy in scattered molecules, significantly less than phonon losses. Vibrational excitation and deexcitation of scattered molecules, while remaining a minor pathway for energy flow, is strongly affected by the inclusion of ehp excitations. Finally, although equilibrium diffusion constants are unaffected by the inclusion of coupling to ehp, it causes a significant quenching of transient mobility following adsorption of translationally hot molecules.