To go slightly off topic for a second, these 'parent & child' bays are very often so vague as to their terms that they would be nearly impossible to enforce. To use a slightly silly example, if I take my partner's daughter to the supermarket, could I use the bay, or would I be bang to rights because I'm not her dad? (I never do use these bays, for clarity, she's old enough that we've no need for them).
But, in this case, far easier to go for the lack of keeper liability angle, and use the template that you have already found, and linked to above.
