You won't harm the yeast...those that don't have stir plates shake the crap out of their starters whenever they walk by. As for cold crashing and decanting it depends on the time you have. I usually dump the whole starter, but starter beer does not taste great. So some will let the starter run for 24-48 hours, put it in the fridge overnight to speed the yeast settling out, pour off the starter beer leaving enough to swirl the yeast back into the liquid, and just pitch the yeast. Done it both ways and have not noticed a difference adding 1.5L of starter beer to 5-6 gallons of wort. YMMV.