Are the questioner's children entitled to anything from the proceeds of the waqf endowed by their grandfather, knowing that they are from the second class (children of children)?

If the grandfather endowed a waqf for his children and his grandchildren, generation after generation, then the questioner's children are included in the waqf. To determine whether they share with the higher class or after its extinction, one must refer to the wording and conditions of the waqf, because the disposal of the proceeds depends on what the endower stipulated, whether it is equal distribution, preference, or a specific order. If the wording is "for my children, then for their children," then it is a sequential arrangement. But if it joins the child and the grandchild with the conjunction "and" (wa), then everyone shares. It is necessary to refer to the Sharia court to identify the beneficiaries and their order.