Which valves should I close when blowing out my sprinklers for the winter?
Your plan seems reasonable.
Some things to note:

The four little stubs sticking off the bottom are valves - probably ball valves. They could have water trapped inside the ball, so you'll want to blow those out and/or leave them open when you're finished to prevent the valve itself freezing.
The main valve is also a ball and will have water inside it too. There should be another valve somewhere in a freeze-proof location -- either inside the house or a few feet below ground out in the yard. It's find to close the right-hand valve here while doing the blow-out, but you'll want to leave the upstream valve closed and this one open when the job is finished.