Current Atlas and another place to stay
You should get a copy of the Canadian Juan De Fuca Current Atlas, and a set of the tables that go with it. The current atlas is good forever, you need new tables every year. This will really help you understand the farily complex currents in the San Juans as well as the Gulf Islands, and the Strait of Georgia when you start to go further. They never go the direction you expect, and they can run up several knots. If the current is with you, you will make much better time. See attached link, but I'd recommend getting it at Captains on 15th NW in Interbay. Great people. September is a fine time to go, the weather should be good, and since the kids are back in school, you will find lots bouys available at the state parks, such as Echo Bay on Sucia and Reid or Prevost Harbors on Stewart. The bouys are nice, espcially are new to anchoring, because you always sleep better if you don't have to worry about the anchor dragging.One of my personal favorites has already been mentioned: Pelican Beach on Cyprus Island is very pretty, with a nice hike to the top of Eagle Cliff. This is a popular spot with kayakers (which is how I found it). Please note - do NOT anchor here, you just can't. Its too steep a drop off. But there are about five DNR bouys, so if you can get one of those in settled weather, its a great place to stay. As mentioned by others, you must go to Sucia Island, and marvel at the fact that the island was purchased by boaters and given to the state for a park. Echo bay has a great view of Mt Baker. Its a long way in a week, but doable, so that should be your goal. Have fun!