we are cruising out of seattle in may,?

Yes that should be fine. You can't get on board until noon anyway so let's say your train is over an hour and a half late, that gives you the time for the cab and boarding and you should be on by 1pm. You need to be on board usually 60 minutes before but that depends on which line you are with so let's say it's done boarding by 3 (which is really early--so I'd verify that with the line).

Trains are usually late but very rarely is it 5 hours behind schedule, which is how late it would need to be before I'd get worried.

Myself, I wouldn't chance that arrival/departure. It's a good idea to get to your departure port the day before, to allow for delays, etc.

You may be fine, though....