Heading downriver from South Bend, WA is fun because there are a few sloughs which are fun to explore if the tide is coming in and there is enough water. A couple of hours before high water is great; you will be greeted by local seals and if you are lucky you will come face to face with a bald eagle or two. You may travel farther downriver and venture up Smith Creek or North River.
The Pacific County Historical Museum, located in South Bend, has some great maps of the Willapa and surrounding areas for kayakers. The man I talked to there, whose name is Bruce, had quite a bit of general information about the area as far as kayaking goes.
Paddling upriver from South Bend is the city of Raymond which is about a leisurely 2 hour paddle with the tide. There is a boat launch at the 8th Street Park at the north end of town. There is no fee to use the facility.
Continuing on from Raymond, the Willapa River heads upstream for many more miles and countless hours of leisure paddling. Even if the tides are against you, it's still a pretty effortless paddle from Raymond on upstream.