I think anyone who has dealt with trump for any amount of time longer than, say, a week doesn't remotely rely on what Trump tells them, "Don't worry," he'll do. They KNOW -- just as well as you and me -- all the lies Trump has told on the campaign trail and daily in the Oval Office. They KNOW all his promises that he has backed out of. They KNOW his history of screwing anyone if it's to his benefit (and make no mistake, they know that Trump may well be given the advice that too many pardons could be seen as obstruction of justice) -- and so they have no idea who Trump will actually pardon when it comes down to it, until the paper is sign, sealed and delivered.
People who *don't* know Trump know his word can't be relied on. People who DO know him KNOW that as being Rule #1. The only message Donald Trump ever actually sends is -- I'm unreliable, and can change my mind in the middle of a sentence, and I'm the only one who matters to me...ever.
And I include his children and son-in-law in this. They certainly are the most-likely to expect that they really will get a pardon. But they are also the most-likely to know that absolutely nothing is certain with their father, and if he can save himself by screwing anyone -- including them -- he will.
As a result, anyone called to testify KNOWS that they'd better cut the best deal they can -- if offered -- rather than wait in anticipation of a pardon. A pardon could come after that -- but if they testify against Trump, I wouldn't count on that. And if Trump pardons them before they testify...well, then you can start the countdown to obstruction of justice charges for impeachment.
Of course I think most of the Trump inner circle do believe they are likely to get a pardon. And I think that they are likely to get a pardon. But I also feel quite certain that they more than anyone know that his word CANNOT be relied on. To be very clear: I'm not saying they will testify against Trump -- I'm only saying that they know that any "message" of a promise Trump supposedly sent is meaningless. Because they know any Trump "promise" is meaningless.