Can you see your raiding party in real time on the mini-map?
From toady's comments you can't see them in real time but you will get information of the journey dispensed via rumors & confirmation when they arrive back (or fail to arrive) along with information on the locations along the route.
Can you raid kobold sites? If so, will they send full-blown retaliatory ambushes like other civs?
Do kobold bring mounts with them in ambushes/theft attempts? What kind of mounts do they have now?
Can you raid sites for no reason whatsoever (i.e. without an artifact or a kidnapped baby to retrieve/rescue)?
Yes to all of the above, this was covered in
Toady's latest FotF reply with a giant cave spider called lurbin, assumedly creatures that can be mounted will be brought along too. Generally also from toady's comments wandering into a settlement for no good reason will prompt a imminent raid or attempt to reclaim/steal a artifact there.
As to the cave civ question, i dont think toady has put in the ability to travel via the subterreanean world edges so it'd be unlikely and cave civs are sparse & poor anyway.
Can you raid necro towers to retrieve their books about the secrets of life and death (considered artifacts)? Can necros retaliate in response?
Can you raid non-civ specific sites like shrines, labyrinths, lairs, etc.?
Stands to be seen when the actual release drops, but there was slab related questions a while ago and the object will belong to the necromancer (and since the necromancer owns the tower site, it is likely). I personally wonder if outcasts that sometimes hide in these worldgen minor places might attack as local resistance people besides the monsters that could reside there.
There's another good chance they might not actually be places your party can visit yet or won't find much reason to visit there again after clearing it out once.