FWIW if you look at previous years test fisheries and hydroacoustic data it's pretty consistent that the first ones will show up in the Fraser sometime mid-august but not many. I dont have it in front of me, but I ran some numbers in previous years based on test fishery data and I recall that something like 10-15% of the run returns in Aug and the vast majority won't be until the first three weeks of september
Unless I'm mis-remembering, the largest 7-day rolling return period in the Fraser test fisheries is usually in the second week of September (ie Sep 7-14 +/- a few days). It's not unusual to see 40%+ of the total test fishery sampled during that peak week. By the last week of Sep, the run is basically done in the lower Fraser.
In 2023, tidal and non-tidal waters of the Fraser opened on Sept 1
In 2021, tidal Fraser opened Sept 3, and to your point non-tidal opened on Sept 11
The Fraser was closed in 2017 and 2019
In 2015, the tidal and non tidal Fraser both opened on Sept 5.
In 2013, the tidal and non tidal opened Aug 30 and Aug 31 respectively.
Based on this, if there is an opening it seems that it's typically early enough in Sep that there will still be plenty of time for you all to hit the bulk of the run. Plenty of fresh ones to be had, especially if you are able to hit the lower Fraser or the salt.