The handshake was a great moment.
I also loved when they went up the beanstalk and had to climb up on that huge table. Hook asks if David would trust a pirate to do it and David responded with by saying that no, but he would trust his son.
Killian's answering eyebrow raise and David's little smirk when he adds "in law" made it even better. Like they've come a long way, but they're still them if that makes sense.