PDCheque issued as surety for a handloan - Beneficiary absconding

One of my brother-in-law was running a Milk Parlor. Due to various reasons he has borrowed around 6 lakhs from 20-25 lenders including private financiers, he was unable to manage this since the interest rates were exorbitant (say 5% to 10% pm). He ran away sometime in January and called my wife, informing the same, and my wife started crying and shared this information with me. On humanity ground, I asked him to meet me and thought of helping. I understood from him that, his daily commission is around Rs.1100 to Rs.1300 (monthly income is around Rs.40000/-). I cross checked the same with the Manager of the Thumkur Diary (Principal) and it was true. Then I went one step ahead and paid the dues to the Principal amounting to Rs.49000/- and also paid the rent of his house (Rs.6000*2=Rs.12000) Then I personally went and met most of the lenders and briefed them about his situation and requested them to give him some time and he will repay your debts in 2 Installments without interest (one in May & the other in December) and also told them that I can act as a surety for the same. Some of the lenders agreed and some disagreed (everything was oral and nothing was reduced to blank and white), with this he was able to run the milk parlor for another 4 months. Later we don't know what happened, in the month of April, he is absconding. And now, the lenders are calling me and my wife over phone and demanding the repayment. I don't know, what is the remedy available for myself and my wife under the law. Another thing is that, of those 20-25 lenders only for one lender I have issued 2 post dated cheques as surety (dated 30-May and 31-Dec) and nothing else apart from the cheque is given to this lender. Now, please advise how can I come out of this situation? Am I liable to honor the cheque or is there any remedy for the same? Thanking you in advance.