I believe in prewashing and I think you will do just fine with the 10" squares. Put them in lingerie bags if you worry about it, but I think you could just layer them in with a light load of laundry. There may be a bit of unraveling, but it won't shred any more than a fat quarter would.
The drying and pressing now... that I would be watching so that you don't end up with hard little wads of fabric dried into concrete. Snap out each square as you take it out of the wash and put it in the dryer. Dry for half the time you think and check on them. When they are just almost dry, take them out, snap them again and stack them and press them immediately.