It will be rainy on the coast; snow would be pretty unusual. Of course by traveling in mid-December instead of early November, the days are going to be even shorter.

Working backwards, you'll need one overnight between Santa Rosa and Las Vegas, so that would be the 22nd. Staying with your friends in Santa Rosa on the 21st, that would give you four days (or, say, 3 nights) between Victoria and Santa Rosa, one more than you had last year.

In which case, I'd probably (a) follow 101 on the east (Seattle) side of the Olympic peninsula rather than via the west side, and cut over to the coast at Olympia. The weather is more likely to be dry(er) then going through Forks et al, and the going a bit faster. Stay the first night in Astoria, or, frankly, if the weather is okay, just stay on I-5 south of Olympia and cut over to the coast further south, at Longview or even via Portland.

I like Bandon a lot for the next night, then I'd take it really easy the next day, enjoy the Redwoods and the southern Oregon coast, and end up in Eureka the following night. That would give you an easy day into Santa Rosa.

Santa Rosa to LV is boredom city, but easy enough - cross the San Rafael bridge (I-580) and stay on I-580 all the way to I-5, then south to California 58 (Bakersfield-Barstow freeway) to Barstow, where you join I-15 into Vegas. I'd stop in Bakersfield overnight; it's a little more than half way but is the most convenient place on that route. Get an early start the next day because you'll still have 4-5 hours to get to LV. Or, if you want to make it a bit harder on the 22nd but easy on the 23rd, push over Tehachapi Pass on SR 58 and stay in Barstow. (If you're going to encounter lousy weather in the California part of the drive, it might be at Tehachapi Pass, where it can be very windy and/or even snowy once in a great while, so crossing it in the late afternoon might be preferable.

I've only spent one Christmas in Las Vegas, and it was... weird, so no guidance there. Have a great trip!