The role of wake effects in the charging of dust grains by plasmas with subsonic and supersonic ion flows is studied with numerical simulations. Significant ion focusing which is common for supersonic flows is also observed for subsonic regimes. In both regimes, the charge on a downstream grain aligned with the flow depends linearly on the intergrain distance. For subsonic flows and systems with several grains, the complex ion dynamics can lead to significant modifications of the charge on grains located close to the boundary of a dust lattice and the charge distribution on the grains depends on the detailed grain arrangement. The studies are carried out with DiP3D, a self-consistent particle-in-cell code.