For all of us in WA: SEA-BCN, 2 adults, 1 child = $619. Amazing -- we beat LAX? Well, OK, it's only $5, but how often does that happen.
If you haven't already, check out SideStep. GREAT travel search engine (SideStep.com).
Keep in mind (I'm a TA, and I try to remind my clients about this when they book Europe): Most flights from the US will get to Europe the NEXT DAY. Be aware of this when it's time to book air. If you book a flight on the 18th, chances are you'll get to BCN on the 19th (unless it's a midnight flight). GrayFal, your flight arrives on the 19th
Keep in mind that if you're trying to catch a ship, and you're NOT going through
DCL for air, they won't wait for you if flight delays keep you from boarding. I recommend booking a flight out on the 17th at the latest, unless you're going through DCL or taking a midnight flight on the 18th (and that's still risky). Also remember that midnight on the 18th comes at the end of FRIDAY, not Saturday. Ask me about people who book midnight flights and get to the airport the night AFTER their flight was scheduled...
This ends the public service portion of our show. Nothing to see here...move along...