well, any indication from last year when I went close to that time, and last week, you should limit in halibut 10-20lb, and will likely see non-stop coho action on the surface (like 10-20+ hookups). Only question mark will be chinooks. Last year, most our boats slayed them out at the banks on plugs (up to 28lb), and that could be the case this year too as there is supposed to be a windfall for Oregon fish passing that have to pass through...if they aren't there though, you should do fine at the beach. Last week it was non-stop action after we got our halibut - after 10am to noon, but often, if you choose to go out to the banks, if you come back to the beach around noon, its very hit and miss.
Trust in your guide and their recommendation, but figure out your purpose - if you want your shot at a 40+ salmon, you may have to start at the beach in the morning, but run the risk of it getting too windy after to get to the banks for halibut. Is it worth the sacrifice? If you want a 50+ halibut, you will likely have to go to a different location and anchor - it will be slower and more time consuming, leaving little time for salmon. If you want non-stop action, regardless species/size, go straight to the banks.
Remember your gravol as well, especially for the mrs. - nothing worse than their stomach turning and insisting that you return - our trip last week, I think about 6 of 15 were sick, one was quite severe. Was apparently roughest of the season though.