Changing My Family’s Last Name, Easily Done Or A Huge Hurdle?

My husband and I are married with young children. We reside in Virginia but he is a California resident (military). My husband was adopted as a child by his then newly step dad whom he has no relationship with. Fast forward, my husband and our family have a beautiful relationship with his bio father and bio family for decades. Now that we have children we are considering(still pretty young enough to barely know they will have a different last name) changing our last name to his bio dads. What’s the process look like for this, mostly given that we reside in Virginia and he’s a California resident while I am a Virginia resident. What would fees look like? And anything I should be made aware of?

He has all legal adoption paperwork from when he was a child, along with a paternity affidavit stating his bio dad.

I know I don’t have to explain myself or our personal reasons of doing this, but we just want to do what we feel is best for our children. We want to avoid the conversation with our kids about how we have this last name but those people don’t care for us or to have a relationship with us.