The basic features of ion-acoustic shock waves (IASHWs) in a multi-ion nonextensive plasma (containing positive light ions, negative heavy ions, as well as nonextensive electrons and positrons) have been rigorously investigated in a nonplanar geometry. The standard reductive perturbation method has been employed to derive the Modified Burgers (MB) equation. The combined effects of the electron and positron nonextensivity, and the ion kinematic viscosity significantly have been found to modify the basic properties of these electrostatic shock structures. The properties of the cylindrical and the spherical IASHWs are observed to differ significantly from those of onedimensional planar waves. The findings obtained from this theoretical investigation may be useful in understanding the characteristics of IASHWs both in space and laboratory plasmas.