Oomnis, it depends a lot on the way it is doen. If someone critisises her dil and tells her that her children look neglected, and she wants them to wear different shoes on shabbos, or “there is now ay they arre coming to the chasuna looking like that” then they are asking for trouble.
Yes, a caring and doting – and responsible bubby can buy her grandkiks shabbos hsoes, but it can also be done very wrong.
Remember slao that if the children live abroad or in a different community, they may feel uncomfortable standing etc…
Bottopm line, it all depends on seichel