[Avodah] inviting the grandparents Z"L to the wedding

[Shoshana L. Boublil]

I was asked the following question by a bride.

She intends to go to the kever of her grandfather to give him an invitation 
to her wedding.  When should she do it?


As a Litvak, I've never heard of this myself, but I recall rumours of 
something like it in other places.

Does anyone know anything abou this?

Thank you.

Shoshana L. Boublil