I have 10 days before I can book port adventures and any onboard activities for a cruise in August. Is there somewhere that I can see what is available ahead of time? Can you see which activities are already sold out?
Not until after your booking window opens. (I can pretty much guarantee there will be NO cabanas on Castaway Cay - family OR Serenity Bay (18+ only) though.)
Unless you’re in a meet-up group somewhere with people who can already book and they can check for you.
The website will show excursions and tastings that are options for each cruise but I can’t remember what tab it is. Is that what you are asking so that you can research options? It won’t show if they are actually available or have spots until your booking window opens.