I would like to donate a sum of money to my grandchildren, but I am 82 years old, is it still possible?

Yes. It is always possible to make a donation, regardless of your age.
However, the beneficiaries of the donation will not be able to benefit from the special allo-wance of 31,865 euros applicable to donations of sums of money (from article 790 G of the General Tax Code) granted in particular to grandchildren.