re going down the west coast of the States--your bike has a low of 28.4 gear inches, when I did that trip many moons ago, I had two lower gears than you, 24.7 and 21.4 and was certainly glad of them many times. There is a lot of short steep ups and downs at times, and just take into account that although you found a 17% fine with trying out a ride with all your stuff, there will be times when you aren't as fresh as on this test ride, and you will wish you had lower gearing.

I realize that because you have a road compact crank on your bike, its not an easy change to get lower gearing, short of changing out your rear derailleur and getting a larger rear cassette, so you don't have a lot of easy inexpensive options.
How much does all your stuff weigh? I suspect your total load is less than what mine was (mine probably 40lb) so just be aware of keeping your load at a minimum. I was in my 20s at the time, and was still glad of the lower gearing on that trip, and recall that the west coast trip was harder climbing than biking along most of the Pyrenees the summer previous (longer climbs, but not as steep gradients).

have a good trip, hope it goes well, its a very pretty ride. Bikes with triples have a big advantage for touring and making it easier on your knees, so I guess just take this trip as a learning experience and adjust afterwards for how you see it goes with X gearing and Y bike weight for the types of hills you'll be on. If need be, walking isnt the end of the world and its easier than mashing too slowly which is hard on your knees and not good for long or short term knee stuff.
cheers