"Any target that isn't a Dinosaur" means any non-Dinosaur creature, any planeswalker or battle, or any player (no matter how old they are).

If multiple sources deal damage to a Dinosaur you control while you control Wrathful Raptors, most likely because multiple creatures blocked that Dinosaur, Wrathful Raptors's last ability triggers only once.

If lethal damage is dealt to a Dinosaur you control while you control Wrathful Raptors, Wrathful Raptors's last ability still triggers.

If Wrathful Raptors and one or more other Dinosaurs you control are dealt damage at the same time, Wrathful Raptors's ability triggers for itself and for each of those Dinosaurs, regardless of whether or not Wrathful Raptors was dealt lethal damage.