So sorry to read your post. This latest news must be like a knife in your hearts, opening the wound.
Could you focus on your daughter and grandson and think that your son-in-law died helping a terrible situation? Easy for me to write, I know.
The problems in Afghanistan are likely to be on-going for many years to come as there is no quick fix and as Deedaa said, the Russians, with all their resources, failed to beat the Taliban.
Please try to be re-assured as our troops will not be actively fighting but in an advisory role so hopefully they will be in less danger.
Don't let this news win over the good things that you do and experience, otherwise 'they' will have won.