I think it is lovely to see her looking genuinely happy and having a good day. She's 96 and doing well for that.
That she now has mobility issues is not at all uncommon at her age. My mother is 87 and can't walk far. She can shuffle around her house, but needs either her mobility scooter or her wheelchair when out and about, with myself or my sister to hand.
If you have never suffered with mobility issues or had to take care of someone who does then you might not see the walk through the Palace of Westminster to her throne (up those steps) in the House of Lords and back again as an issue. Believe me, it absolutely would be.
The Queen doesn't want to use a wheelchair or scooter in public. That is her choice to make. It wouldn't bother me at all if she chose to use them, but she is trying not to.
I seem to remember that the late Queen Mother did have a mobility scooter for use in private on royal estates. It wasn't used publicly very often, but she did once or twice use it for her traditional birthday appearance outside Clarence House when she was a similar age to what the Queen is now and walking was difficult for her.
I think it is great that at 96 the Queen is now delegating a number of her more onerous duties to Charles and William. She needs to do that, and they are both more than capable.
Reaching her platinum jubilee is a great thing. It does mean though that she is no longer a spring chicken and reasonable adjustments will have to be planned for. It is uncharted territory for all concerned as she is now the longest reigning monarch we have ever had. There hasn't been a platinum jubilee before, so no real precedent.