I agree, juney - that seems sensible as a general rule, though of course one can think up situations in which a specific parent's needs could be greater than those of a specific disabled person.
And wrt the Parent and Toddler spaces being obviously for toddlers not 9-year-olds, I'm pretty sure that these spaces are still not always labelled parent and toddler, but can still be labelled Parent and Child - and if that were the case for the lady in the article, well - a 9-year-old is clearly still a child.
I'm going to be looking whenever I see P&T spaces to see how many are clearly labelled as being for parents with toddlers, and how many are less clearly labelled.
Let's not forget too, that Parent and Toddler doesn't cover all those who could use such spaces with justification - a grandma out with her grandchild, someone with a friend's toddler, a parent with a non-mobile baby - all of these can be said to fall outwith the narrow catagory of a Parent with a Toddler, but would still be most ble to use these spaces, imo!!