I cannot speak much about another option on the Northshore, but Northstar for a day would be fine. Ride the backside. Alpine and Squaw can keep many entertained for a number of days.
As for the south shore, Ride heavenly for a day or two, spend a day at Sierra At Tahoe, and at least two days at Kirkwood. I'm all about checking-out Variety, but you may be spreading yourself thin trying to hit 6 mountains in 8 days. You may be just as well-off getting an Epic and riding Kirkwood, Heavenly, and Northstar.....all on the same Pass.....Or Squaw, Alpine, and Sierra at Tahoe (all on the Same Pass)
Also, you're looking at quite a lot of driving To and from between the south shore and the north shore or even Kirkwood. (Though I always endorse going to Kirkwood.)
Let it Snow, Let it Snow, Let it Snow.