Plastic bags with handles make great temp pots for moving plants around. Whichever method you choose, store plants in a little more shade, so they don't cook/bake to death while waiting to go in the ground.
IME with mulch, it's easier to place after plants are in place *IF* you have enough pots that are big enough to cover plants, or you can keep using the same pots by working in sections. With an pot upside-down over a plant, you can mulch around it so easily.
