Is it necessary for the children to re-obtain a deed of inheritance limitation after the death of their guardian and grandmother, given that the grandmother was not included in the first deed, and neither she nor her children claimed their right then or thereafter?

Your paternal grandmother's share is one-sixth of his inheritance if the deceased has no mother, by the consensus of the people of knowledge. The grandmother's or her children's failure to claim their right does not nullify it. It is necessary to verify if the grandmother waived her share or agreed with your uncle; otherwise, her right must be delivered to her heirs if they do not waive it, in order to clear the conscience and uphold justice.