1. Restore first, still in black and white
Color can only be as good as the picture underneath it. A speck of dust colorized is a colored speck; a crease becomes a bright line across a cheek. So the first pass removes dust, scratches, stains, creases and film blemishes and evens out faded tones, while the photo stays black and white.
Nothing else is allowed to move. Every face has to stay the same person, with the same features, expression, age and pose, because a restored stranger is worse than a damaged relative.