These three will be listed together, as they are not given sufficient characterization to distinguish them from one another. Cooper (John Diehl), Nash (Bruce A. Young) and Udesky (Michael Jeter) are a trio of mercenaries recruited by Paul and Amanda Kirby (William H. Macy and Téa Leoni). They are all quickly killed once the cast reaches Isla Sorna. Cooper is the worst and takes out Alan Grant (Sam Neill) when the good doctor objects to the landing. So he goes first, devoured by the Spinosaurus. Nash follows him shortly afterwards. Udesky, on the other hand, is killed by a pack of Velociraptors, with the dinosaurs using his corpse as bait to lure the others.
Again, with such a thin characterization spread across the three, it’s hard to say they necessarily expected it. “Jurassic Park III” seems to have the illusion that we care about the Kirby family, so the mercenaries are there for the same reason that Red Shirts exist in “Star Trek”; they are disposable “good” characters that can catch the trap for the main characters.
In-universe, all three of them accepted the job to go to the remote island full of man-eating predators. Even for career mercenaries, that’s a dangerous, suicidal assignment. In other words, they knew the risks and paid for the consequences.