I'd also bring hearing protection if it were about my daughter, but - from a medical point of view - is a child's ear really more susceptible to hearing loss than that of an adult? Seems like concerts nowadays aren't that loud anyway, DT especially. I saw them in an outdoors venue, but could easily hold a conversation in the fourth row, and the crowd's singing often overpowered the band itself. The mix was great though.
As for other dangers, DT fans are mostly nerds anyway, who watch the band play in awe, I wouldn't worry about any moshpits ensuing.
Also, speaking from personal experience, seeing a rock show at that age could easily prove to be a life-altering experience.