I was wanting to go down this week again, but the heat had me questioning that. Maybe I still will. When it's this hot, I get torn between a trip to Deep Creek or a trip to the ocean.
On some more specific of the OP's questions: There is plenty of shade down there. Many trees all along the creek provide shade. There is even one pool now, the newest pool, in the shade all day and it is a pool with hot spring water temps only in the 90s. When it is this hot, soaking in the pools is more for early morning or after sunset, in my book. The creek will not be cold, but in this heat it will still feel refreshing and you'll probably be swimming in it all day. Camping at Bowen Ranch: no amenities, just some white picnic tables and some fire rings at different camp spots near the parking area. There is one relatively secluded "valley" camp site, that you can't see until you walk or drive down into it, I guess it is just to the left as you drive into the main parking area. (You can drive a car down into this valley and there is a picnic table down there; it's the most secluded of the spots.) I like camping at Bowen Ranch - sunsets are beautiful there, mornings too. The only problem is it can be windy at times, and it is somewhat trashed or has been when I've camped there. It would be great if the Ranch would clean it! Greater still if folks didn't trash it in the first place. But it's definitely your best bet for camping near the springs. There is not much shade up at the Ranch; but mostly I'm there at night so it doesn't matter. If a group is there to party, you will not have quiet nor privacy. You can be nude at the Ranch, in the camping area as you can be down at the springs and many campers are FYI!