I don't do the dining plan anytime, but I especially won't do it during the festival.
Whether it works for anyone at that time would depend on how much that party is planning to eat regular meals at restaurants, so you'd have to decide how much grazing at the festival appeals to you. You can use snack credits to do so, by the way, so a lot of festival-goers purchase the quick service or deluxe plans with 2 snacks per night.