Wiring receptacles to light switch
If you take one long 12/2 wire directly from the source to the switch and then connect from there to every receptacle, then it can all be done with 12/2. However, if you plan to take the wire from the breaker to an outlet first and then eventually the switch, you'd have to run 12/3 between everything but to the breaker and wire nut the hot together all the way until the switch.

You can do this all with 12/2.