We employ mixed quantum-classical molecular dynamics simulations to investigate the fragmentation of N2 molecules after core-level photoionization by an x-ray laser, subsequent Auger decay, and followed by a femtosecond IR pulse that interacts with N22+. The delayed IR pulse couples the dissociative electronic states of N22+ with electronic states that can support long-lived vibrational resonances. We compare our simulations with previous quantum dynamics calculations in a quasidiabatic representation, which employed a small number of electronic states. Good agreement for both the Auger spectrum as well as the influence of the delayed IR pulse is found. By employing the mixed quantum-classical treatment, we can greatly reduce the computational cost to simulate the fragmentation dynamics compared to the quantum dynamics simulations. Furthermore, we reinvestigate the title process by employing an extended set of adiabatic potential energy surfaces and also investigate the role of nonadiabatic coupling in the process. The use of the full set of adiabatic potentials increases the dissociation probability and changes the details of the interaction with the IR pulse, but no effect due to the nonadiabatic coupling is found.