Actually, JoAnne, you said it perfectly. Maybe that's why we like cruising with you. When we do, we each go our way and if we want to do something together, we do and we don't have any obligations so we never have any of the stress of "oh, we have to do what they want". We can say we want to go do "X" and no one feels bad. Hey, when you are spending $5,000 or more for a week's vacation, it's still your vacation and you can still share the experience. Same goes for spouses, while we love them dearly, do you ALWAYS want to spend 24/7 with them? We can sday lets have lunch today or not, let's have cocktails before dinner or not today. No pressure.

As for booking things, I agree with JoAnne again. Maybe you want to fly (Which is now about $300 per person) and maybe they don't want to spend that kind of money or have that experience.
It's always fun to compare at cocktails or over dinner when you've all done different things too!

Editing to add that there are things you do have to book ahead, but, you can give everyone their own choices. Tell them what you are doing, tell them you would love the company and give them the freedom to check out the things they want to do without obligation.