Dunno if the druids bother heading there on Samhain. They might. If so there's some entertainment for you :-) With it being a bank holiday it should be busy.

I hate going up there on special occasions though, because I end up getting tetchy with all the idiots that light fires all over the hill.

Lough Gur is a good choice if you're down that way, but you might consider Duntryleague. What a view to the north you get there! In fact I might just do that instead :-)

The mound of the hostages has an alignment to the samhain sunrise, I've never seen it or any photos of it though its supposedly more accurate to view it on the 8th November. Only reason I would go to Tara for Samhain is if the gate is opened to see the carvings etc better.