I haven’t got enough time on my hands right now to review the whole desingn, but one thing that jumps to mind is that you’ll want to use an antiparallel diode on each relay coil to suppress the negative voltage spikes when switching it off.
Be sure to keep adequate distance between high and low voltage traces. The ground plane seems awfully close to the N trace.
Other than that, I’d happily welcome more PCB and/or personal project discussions!