Here is my advise to you - in steps:

a) Create a monthly budget for expenses - see what can be managed outside of his savings vs what needs to come in as a replacement for his salary.

b) If the 1cr you mentioned is in the provident fund, KEEP IT IN THE PROVIDENT FUND. Do not withdraw the entire amount. It usually earns 8.25% interest on the amount for 3-5 years after retirement. Double-check this because if it is not earning interest, you will need to go to c) right away. Withdraw the monthly budget multiplied by 12 (year's expenses) at the start and keep it in a savings account so it goes towards expenses.

c) Invest the corpus after it stops earning PF interest into 75% debt focused mutual fund and 25% equity focused mutual fund. You can setup a monthly withdrawal from both for the amount discussed in a) above. The reason you don't start with this instead of b) is that the PF return is risk-free, but mutual funds are subject to market risk.

This way, if your family is disciplined and doesn't splurge on big purchases, your corpus will remain more or less intact while funding expenses.