So here is the thing you can be the best photographer in the world but if your subjects aren’t having fun then your images are not going to be the best they could be. Play and have fun while working and your images will go to the next level.
I have been on countless photoshoots for everything, newborn, engagement, wedding, commercial, marketing, modeling, literally everything and my best images always happened when the person/people before my lens were having fun. You can see the depth of that joy and happiness in the images you make, in the mirth in their eyes, and body language.
Yes; even on a serious shoot you can have fun, even in war torn countries photographers on the ground in war zones have more images than carnage they have small captured moments of camaraderie and joy that is eked out in devastation.
Play while working your images will thank you for it.