What is a grandmother's role?

My mom and I are struggling to find a balance. I don't want to give up aspects of motherhood like making his birthday cakes and taking him fun places. I didn't have involved grandparents, my mom had to beg my grandma to do things. So what are grandmother's "supposed" to do?

Add on: it's hard because I didn't have involved grandparents and she didn't have involved parents. Her parents were abusive and her grandmother was her only shelter from that. I did not and do not have a good relationship with my mom. We're working on it but it is very strained. I wasn't raised to know good and approroate boundaries becuase my mom doesn't know them.