We report on a theoretical study of the electronic, optical, and magneto-optical properties of digital ferromagnetic heterostructures based on Mn delta-doped GaAs. We consider different structures corresponding to Mn contents within the range 12%-50% and we study how the system changes as a function of the doping concentration. Our first-principles approach includes the spin-orbit interaction in a fully relativistic pseudopotential scheme and the local-field effect in the description of the optical absorption. We show that Mn d-doped GaAs shares many properties with the uniformly doped Ga1-xMnxAs system, i.e., half-metallicity, similar absorption spectra, and moderate Kerr rotation angles in the visible spectral region.