The Daoine Sidhe are mentioned in passing during Turn Coat. Specifically that the Edinburgh head quarters of the White Council was won from a lord of the Daoine Sidhe by the original Merlin.
So I did a little research and the Daoine Sidhe basically sound like the group of Wyldfae Sidhe. Not sure I would go so far as to say a "court" but definitely a loosely affiliated entity. If it weren't for his Goblin court, I would say the Erlking would be a Daoine Sidhe. Also "Daoine Beaga" translates as "little folk." A thought just occurred to me, could the Daoine Sidhe be the nobles of the weefolk? Could Toot-toot be on his way to become a Daoine Sidhe?
I imagine some Wyldfae Sidhe would be somewhat paranoid (not enjoying the umbrella of Summer or Winter), and are a good group to be sponsoring magic. "Effect change without presenting yourself as a target? Where can I sign up?"
Changes also brought up the idea of the more powerful Nevernever Entities being scared to leave their centers of power (home field advantage is what tips the balance in the major league). Which further reinforces the reason for funneling power through emissaries. These are "immortal" entities, death doesn't come to them very often (see White Night when the assembled White Courts were leering at the duel
).
Mouse definitely gets some magic from Harry. That is the only way the Ice Demon can stay in our world.