Talk with your children about this. What role do they want you to play in the kiddos' lives?
And it's not about "raising" them or feeling burdened by being a grandparent. You are an important part of your grandkids' lives. You are their story tellers, their history teachers, their link to their ancestry.
My mother passed away 24 days before my son (first child) was born. We lost my father when my son was 3 and my daughter was barely 2. My kids will miss out on Poppa's stories and bad jokes, and will miss out on making Christmas cookies with Babci.
Spend as much time as you can with them.