Following recent advances in the manipulation of atoms trapped near 1D waveguides and proposals to use surface acoustic waves on piezoelectric substrates for the same purpose, the potential of two-dimensional platforms is shown. Directional emission of atoms near photonic crystal slabs with square symmetry is used, in the ideal case, to build perfect subradiant states of 2 distant atoms, possible in 2D only for finite lattices with perfectly reflecting boundaries. These allow the design of massively parallel 1D arrays of atoms above a single crystal, useful for multi-port output of nonclassical light, by exploiting destructive interference of guided resonance modes. Directionality of the emission is shown to be present whenever a linear iso-frequency manifold is present in the dispersion relation of the crystal.Multi-atom radiance properties can be predicted from a simple cross-talk coefficient of a master equation, in good agreement with exact atom-crystal dynamics, showing its predictive power. Departing from the ideal theoretical case, possible experimental issues in photonic crystal implementations are also discussed, and an outlook of other relevant modern platforms for 2D propagation of excitations is given.