Whatever you do, get into town the day before the cruise. Driving through Seattle can be jam-packed, and getting across the border can take some serious time.
Also, Vancouver is nearly an hour away from the border, which still comes as a surprise to me even though I've been driving to/from Vancouver since I was 18! While there's a Tim Horton's along that drive, it's not a totally easy one...lots of traffic at times, and to a US-based driver it can be a little confusing (and not just b/c it's in km).
And that's not even counting the rest of the drive and the surprises and slowdowns that can crop up. Just give yourself lots of time, OK? If you get there early, bonus, because Vancouver is beautiful and is worth a bit of exploring.