Oil Nut Marina is a fun stop and we enjoyed a very nice lunch but you can't really get from Oil Nut to the others without going back to Gun Creek. They have a great heated pool and a few shops but overall it wouldn't be worth it for you to take that much time out of your day.
Seems there are always mixed reviews on Saba but we have officially given up on them We have been back a few times since the reopening, most recently a few weeks ago.Food was very mediocre and drinks were terrible. Not to mention everyone there just seems plain miserable. That said, it is an amazing rebuild and they can't really mess up beer and wine. They will taxi back and forth between BEYC and Saba.
North Sound bistro was advertising that they are now doing lunch but I can't remember which days and I don't think they run a water taxi consistently yet. They may be willing to pick you up if you call them though. The folks there are wonderful.
Bitter End is the place you should plan around. Do NOT miss happy hour! Starts at 3PM with drink specials and it is a very fun atmosphere. We did lunch (dinner menu the same and didn't feel substantial enough for us) which was wonderful. You can do watersports there too if you choose.
We were all over North Sound on multiple days our last trip and if I had one day I would hit Bitter End for lunch/happy hour followed by dinner at Leverick Upstairs.