Roger Long wrote:

I think a key point here is the singular. My sons are totally
different people when either of them is with me alone. Together, they
are performing for each other and every nuance of every event is
bouncing off the other. Seeing if they can exercise the power of
getting the other one to do what they were asked to do instinctively
more important than keeping a boat from hitting a dock.

The most vital thing to the future of this boat is getting out with
them one on one but it's a tough thing to work into all the other
family agendas.

I think we all can appreciate this, but I think you cannot afford to
bring personal or family dynamics into a necessary lead/follow
situation which involves actions that control the safety of property &
lives. ISTM you (and they) would be better off to lay out & explain
the entire plan with all participants on the dock and in specific,
behavioral terms before anyone even steps aboard. You may also make it
clear that the plan is in trial, may be flawed, may require subsequent
changes or refinements, and that *you* are responsible for all of it
from beginning to end. This takes less time than to do than type, and
often saves much confusion or conflict aboard, especially when we
ourselves may be uncertain of how our plan will work and may have to be
concentrating on our *own* corrective options to save the moment.
Doing it on the dock also conveys the high importance of it to even
sailing at all, without having to say so.

IOW, it is easy to forget what good leadership is when we are dealing
with relatives or family, and most need it. Some people even benefit
from or need to be shown exactly how to snub or handle a specific line
on a specific cleat/bit/bollard by seeing you do it first. Some even
need to be shown what you may mean by something as simple as "let go."

If you find part of your strategy includes gaining a little sternway
against a slack springer, consider adding your choice of effective line
shock absorbing device, it shines here, and adds some safety as well.
I use a number of similar springline strategies when singlehanding
in/out of tight places & like the black rubber double-dildos. ;-)

As for parenting & instilling patience, cooperation & obedience, it
ended at around age 12 & you have to work with whatever your best
efforts did/didn't produce. If the lady is likewise undermining your
efforts to pull them together, that didn't start with sailing either,
and you did pick her, yes? :-) I suggest solving the latter problem
first, because a lot of expensive boats are sold at very deep discounts
this way. In fact, it's the only way some of us can afford one.