Well, it won't be, according to the school, nor to some people in the forum, but it's for your daughter to use her discretion. I think they are obliged to refuse any requests.
Grandkids other nan lives in Canada. She is ill but it is not terminal. However, it is also her birthday, a milestone one and daughter and kids want to surprise her. Daughter wants to take them out of their primary school for the week to travel to see her, the illness being the exceptional circumstance. Am I right in saying this should be fine?