Travel during winter

I agree. Check the forecast for the super small chance of snow but typically you're ok. I used to have to travel from Seattle to Bellingham/Blaine (northern WA state) in a crappy 2wd g-car without problem. You'll be fine with gas stations on the route. I would warn you that WA State troopers frequently station themselves with radar guns on the shoulder of the I-5 so speeding is not recommended even in rural areas.

Tulalip is decent for an Indian Casino. I second the $5 craps table. I used to also hit up the Eagles buffet though I would rate it as decent. The outlet nearby is huge and I shopped there frequently.

I also never stayed at the casino because the room rates seemed pretty high for what is offered. My friends did spend a night there and were unceremoniously kicked out for being too noisy.

If you are non-US or Canadian, the border will take a little while longer to cross if you need to fill out and have a visa waiver verified. May also be the same on your return into Canada... I've had the 2nd degree travelling both ways on my UK passport when I was on a working visa, less so now I have resident visa in Canada, and a ESTA record for entrance into the US.

Tulalip was relatively pleasant when I visited, and I would go back again if in the area. I don't know the I-5 that well, but snow in Vancouver is relatively rare (it happens every year, but not huge amounts). This makes it slightly harder when it does occur, as folks are less well prepared for it than they would be where Winter means 2 foot of permanent snow.