I posted similar last night, but it didn't work (?) and I think I'd have got a roasting, as it was a bit more harshly phrased than you, OP!
I totally agree that she's an old woman, would be tired, and that she's naturally taciturn and that even smiley people can't turn it on the whole time - which wasn't 4 hours btw, as she 'helicoptered in' a bit later on.
But... She DID look bored, and it was dreadful to be caught picking her nails looking bored when "her" athletes came. It wasn't a random moment, it was just after Team GB entered.
Her advisers and family should know her limits, and work with then. Every time the cameras were on W & K, or C & C, they looked like they were having a great time. Wouldn't the queen have looked happier if she were close to them? And bugger protocol, she's high enough up to say "actually, I'm going to sit next to Will as he keep me awake and laughing". The world would think MORE of her sitting less formally with her family.
Her role as a monarch is, IMO, to represent the country. If she's not up to it (because of her age, not fault of her own) she should retire/abdicate/farm out more duties.
If they know she can't cope with all the ceremony, why not do the jumping in bit, have sporty Will as the 'official' host of IOC, then make a big thing of her leaving stadium at 23:00 to go down to street to say a big 'go for it!' to the UK team? And then slip off home in luxury helicopter for a cup of cocoa.
It was managed badly.