Hi
If we get a half board standard meal plan with our Disney reservation, can we upgrade to a meal with the princesses? Or do we have to pay out of pocket?
You pay the difference. From the DLP website -
FAQ at the bottom of the page: https://www.disneylandparis.com/en-gb/dining/meal-plans/ What happens if the cost of my meal is more or less than the value of my meal voucher in my MagicPass? If the total amount to pay exceeds the value of the meal, you will have to pay the difference. No refund will be issued if the total is lower than the value of the meal included in your Meal Plan. Only 1 Meal Plan voucher may be used per person per meal.