Investigation of spin fluctuation dynamics interactions in Heusler alloys is interesting. Depending on the nature and strength of correlations, these compounds exhibit exotic/novel ground states. In this context, the Mn50Ni50-xSnx (x = 7.5-10) Heusler alloys in the present investigation are interesting to study. Bulk measurements like DC magnetization and AC susceptibility measurements have provided some knowledge about spin correlations/dynamics. From DC and AC measurements, coexistence of super spin glass and antiferromagnetic phase has been confirmed at low temperatures, which is found to affect their physical properties such as exchange bias, significantly. Importantly the microscopic origin of nature of spin dynamics and the possible existence of spin glass and superparamagnetic nature can be probed through the muon spin relaxation technique.