If you can I would defenetly wait till after Christmas for both of your trips. I may be wrong but i don't think sierra makes any snow, so if we don't get much snow they won't have much if anything open. I wanna say sierra didn't even open till early december last year.
Yeah, I've never had much luck with early-season at Tahoe. You're likely to be met with a lot of closed/bare terrain. But you never know. We started holding off until mid/late February. Much better shot at getting good conditions. Nothing worse than looking at all these awesome mountains with closed trails!