Here is an unofficial source for current information. http://www.dairiki.org/tides/daily.php/boa/2023-07-02
The difference between high slack and low slack and the reason that it is suggested that you transit at high slack is the width of the channel. At low slack there is less width and easier to find the rocks.
You will also find information for both Georgeson Passage and Boat Passage on page 126 of the Canadian Tide and Current Tables. Time adjustments in reference to Active Pass are shown there. Remember that all times in the government publications are standard time, not daylight savings time, so you need to make the adjustment for that as well. Information on how to calculate the currents at secondary stations is on page 115. https://waves-vagues.dfo-mpo.gc.ca/library-bibliotheque/chs-shc-tct-tmc-vol5-202301-41085140.pdf
We have transited Georgeson Passage several times and never had an issue other than one time going outbound in Georgia Strait we were met by sizable standing waves. A little lumpy for a couple of minutes but we got through it.
If you are coming from Blaine to Saturna and you don’t have Nexus for all on board, you would need to clear Customs at White Rock Pier or Poets Cove on Pender. https://www.cbsa-asfc.gc.ca/do-rb/services/trsm-sdtm-eng.html
If you all have Nexus, then you have more choices. Cabbage Island would an option but then you might as well go around the south end of Saturna. Horton Bay is another option, it is on Mayne Island just after you go through Georgeson Passage. We have cleared there before, it was a little confusing as there was no space on the dock, so we just floated around close to the dock for 15 minutes, then left when no one showed up. From Gemini’s experience clearing in White Rock a few weeks ago, I’m not sure how easy that is any more. https://www.cbsa-asfc.gc.ca/do-rb/services/nexusmarine-nexusmaritime-eng.html