Hopefully not veering into the egotistical, but thought I'd update all you kind folk who offered such kind words to soothe my angst over what to wear.
The day was lovely, experience was wonderful and we raised a toast to my mom.
The sandals were popped on and off at a park bench which caused
from passers-by 
The trainers (Air and Grace) were exceedingly comfy for the miles of walking.
It was a beautifully sunny day and we stopped at Somerset House at the urban forest installation there which was a delight.
Just wanted to express my thanks to all who offered kind words and advice to an utter S&B amateur.
You're golden.