Well my boys would never have the nerve to think or say that, esp if she is paying and even if she is not they respect their grandparents because we have taught them to respect their elder. Respect those people who helped and did things for them their whole life. They can manage a nice face, maybe not a smile but certainly a nice look.
I am the editor of our school's K-12 yearbook. I also have done the memory book that is just for 8th graders once before and I doing it again this year. I take TONS of candid/semi posed shots. I dont take the class pictures. A lot of my pictures wind up on the school facebook page and website which is used for marketing. Anyway, I struggle every year with kids making faces. The yearbook does not want these photos in there, the parents dont, and the principal doesnt. It doesnt sell yearbooks. I am quite familiar with the middle school crowd and in this day and age, most of them cant wait to be in a picture, of course the girls need to fix their hair real quick etc. But none of them say they dont want to be in the picture but if they do then they can step out. But there are a few esp for the 8th graders where this is not an option and they need to learn to behave bc I can guarantee that their parents will be ticked off if they are excluded from the picture. I get grief when the kid is absent! The middle school crowd can take their gazillion selfies with their tongues out and duck faces galore on their own time. When I ask them to take a nice picture, I need them to cooperate. It is 9 time out of 10 the same brat who will not cooperate until I call them out and say enough, you are ruining it for everyone else.