I think when it comes to family weddings, the "royal" status and pecking order goes out the window and its Granny hosting for her grandchild with the father hosting the evening celebration. Titles and whether they're working royals don't determine how a grandmother feels and treats her grandchildren.
I agree that royal status and pecking order don't determine how a grandmother feels and treats her grandchildren. However, the working royal does change certain things. If we were to go with the route that being working royal doesn't matter, then Zara and Peter really got short changed because the Queen didn't host a reception for either. In fact, for Zara's reception, the Queen is listed as an attending guest. I don't think the Queen would've hosted anything had William and Harry not been working royals and it was an entirely private affair. It's just highly unusual for grandparents to act as hosts when the parents are highly involved and taking charge with the couple.