I do nto travel at the moment in those area's. "IF" I did, I would probably go with a CB style boat, so I could get thru those shallows, and put the CB down when I was in deeper area's. Where I am in Puget sound, I know of only one place that is really an issue, and that is the Swinomish channel, north of me where JRD, Charlie, stilly, erps are. Which will be filled in by 2015 is some money is not come up with to dredge it. Which usually needs dredging every 3 yrs or so.
To me less than 6' of draft would be dangerous, for you over is dangerous for a 40ish foot boat. Just shows the different needs we have for how we sail and where. It would take a 12' raft on a -4 tide to ground in my marina! 100' off the marina you are in 100+ ft of water.
She drives me boat,
I drives me dinghy!