I'm sure you'll have a great time at the Travel Festival. I attended the Tour Alum reunion on January 17th, and it was somewhat along the same line as the Travel Festivals. I've attended Festivals in the past and would have liked to go again this year, but unfortunately I'm working that weekend.
I'd suggest getting to the area early, about 08:00 if possible. There's a nice Coffee / Pastry shop across from the Edmonds Theatre (just around the corner from ETBD), so you could stop there for a few minutes. I always enjoy visiting with other RS fans, and you can be sure that just about anyone you talk to will be there for the Festival.
Most items in the ETBD shop will be discounted that day, so I usually have a quick look in the morning to get some idea on what I might be interested in. There's usually a LONG queue all day, so there's usually no alternative except to wait in line and miss part of one of the Seminars. I've found in the past that late in the day (just before closing) there isn't as much of a line. Rick's staff will all be "on deck" to answer any questions.
Where are you staying? The Edmonds Harbor Inn is wonderful, and within reasonably easy walking distance to ETBD. I enjoyed dining at Girardi's Italian (on 5th Avenue) and there's also a good Mexican restaurant in the same parking lot as the Harbor Inn.
If you're driving to Edmonds, one note on the traffic issues that Chris mentioned. Rather than take I-5 you might consider branching onto Aurora (Hwy. 99?) as soon as possible after leaving Sea-Tac. It may be a bit less busy, although with I-5 disrupted I'm sure many of the locals will be using that as well. Hopefully someone that lives in that area can provide further details.
You'll probably find (as I do) that it's a VERY tiring day, but also very enjoyable.
Hope you have a great time!