Not returning lended money

hello my father had lended money to one oh his known friend around 2 and half years back.

in return he had given us cheques(post dated).

as of now tht person is not returning money anyhow and the cheque dates have passed almost two years .

we kept waiting as we didnt want to spoil our relations with him. now we are sure he will not return back the money. we have proper documents and cheques . what can b done now??

please help?