Check the bags the day before; that way, they'll be waiting for you at WAS when you get there (although you'll likely need to ask someone to help you find them and/or unlock wherever they've been stored). You'll also save yourself any potential hassle of having to show up very early to check them. Also, Amtrak has rather more lenient carry-on policies than airlines do -- pretty much anything that you can carry without assistance can be brought aboard.