How long does pain last/if any, after a mini root c in children?

My daughter is 10 and was told that she needs to have a mini root c in one of her back teeth. Her DDS told us to not even tell her because it would be just like he was filling a cavity and she wouldn't know the difference. Her father and grandma seem to think that she will be in severe pain and discomfort for up to a week after. Who is right? I would ume the dentist since he is paid to know what he's doing, but I can't find any info about mini root cs in children. Anyone experienced this with their own kids? What should I expect? She's supposed to go to Hawaii the day after the procedure with her father so that's why he's worried.