Turnips (roots and greens) usually taste better when they've received a few frosts anyways. Not sure when you get your first frost down there, but yours are a little on the small side for this time of year. I don't know if they'd survive a frost being such tender babies. But if you bring them in and try to put them out later, I'd wait for milder spring weather since they wouldn't probably be hardened off enough to survive winter. Usually the tops on mature turnips will die back some after a hard freeze, but the roots will be ok.
When you thin these, you could even toss the rejects into a salad. That would be tasty and good for you. I would definitely thin those closest to the perimeter because if you get a root to grow on them, it's going to need some room. Say maybe 3 plants to a pot...you'll want to clear the center then too and give them equal space. Looking at it as a triangle, you might even leave 2 or 3 seedlings at each point and give them a little longer to see which ones out of their group is stronger, then thin down to the final 1 per point of the triangle.
I will be interested to see how they turn out. I've only grown them in the ground. Come back in a couple of weeks and let us know, ok!
ETA: Mature turnip tops can be cooked just like kale or collards. I chop mine and either saute in chicken broth, or put them in a pan with a little water and gently cook until tender then top with some vinegar. Some people put in stuff like bacon or onions too. Depends on how southern you are!