[Man-of-the-Wold]

I would agree that if Radagast was a member of the White Council is was in only a nominal, insignificant way, and perhaps he missed meetings.

I do not think that Elladan, Elrohir and Arwen were members. I think among Elrond, Galadriel, Cirdan, Glorfindel, Celeborn, Galdor and Erestor, one has plenty Wise Eldar, anymore and its an Elven Congress.

As for the attack on Dol Guldor, I don't think that bringing together the Three would have been explicitly recognized as part of it among even the participants. The bearers of the Three was a secret until the end of the Third Age, although if Saruman suspected Gandalf has having acquired one, anyone could easily guess where the other two likely were.

As for the attack on Dol Guldor, I believe there may have been assembled an army of Elves from mostly Lothlorien, with possibly another relatively small contingency led by someone such as Glordindel out of Eriador. But I imagine that the main method of the attack was to be carried out through powers vying with Sauron in ways not unlike how Finrod and Luthien fought him. What that would look like I can't really say. It's for the imagination.

Clearly, Gandalf travelled to the vicinity in leaving Thorin & Co. Saruman may have also set up shop nearby from which to project force, and Galadriel was of course already close at hand. Others of the Council or their agents may have gone to Lothlorien, too. I doubt Cirdan did, but he could have sent capable veterans of past exchanges. I think the ending of "The Hobbit" would leave one to wonder if Elrond had actually gone anywhere "physically" in the time between Bilbo's visits, although its quite logically to assume that Glorfindel would have gone forth.

Regardless, of how much conventional military strength was had hand to protect and assist the powers vying directly with the Necromancer, the whole thing probably went off unexpectedly well, because as we all know, Sauron is said to have feigned retreat, as he already was inclined to declare himself in Mordor.