Now that's what I call a cake. Your grandson is soooo lucky!
This reminded me of a story my sister told me about her kids. When they were small she didn't have a lot of money for Easter baskets, but she alway's made sure to buy them a giant chocolate bunny. She stopped when they turned 18 & 19, stating they were getting too old. That next Easter they came in the house and wanted to know where she hid their bunny! Neither were very happy campers...It's all about family tradition.
I don't think your GS will ever be too old for grannie's cake.