you are worried he's not noticed his great-grandmother has died and he'll get a shock at the funeral?
Obviously not this @AnImaginaryCat
It's more in line with what @daretodenim is saying. He's 9, it's not a usual family funeral, it is a media circus.
Both William and Harry have commented that walking behind the Queen's coffin was triggering for them/ that their mother's funeral in front of the cameras shaped much of their lives.
I'm not a fan of the usual royal stiff upper lip at funerals and have been encouraged seeing actual emotion this time round (how many of us would go to a close family members funeral and not be upset!!). However I think 9 is just too young to have to have him in front of cameras, trying to control his emotions and attend his great grans funeral.