Character Dining Reservations

Do I need to make special arrangements for Character Dining at Plaza Inn and Ariel’s Grotto or do I just make a normal online reservation for breakfast?

You shouldn’t need to make specific arrangements. If you reserve your meals, the characters should be there. Just make sure that the characters will be there during the time of your reservation. For example, I believe the princesses are present at Ariel’s Grotto during breakfast and lunch but not during dinner.