Has even one of these people thought about how they’re going to explain to a young child the origin of his name?
You’re not being unreasonable, you’re being a parent. Welcome to the roughest part of the job, where you have to do what’s right for your child even knowing it will come at considerable cost to you.
You do it, though, because your family is placing “all of the burden” on his shoulders. Just his. They’re looking to dump all this historic freight on a baby — blackmailing you with your grandfather’s life! — just so they can keep dodging that painful trip to the mirror. Shame on them.
You needn’t say that, though. Just this: “I agree we all need to heal. It is not a baby’s job, though, to heal us — he comes into the world just as himself, with a clean slate. I owe him that. I think we owe him that. I don’t expect you all to agree but hope you’ll respect our decision.”
If (when?) the [blame] hits the fan, don’t explain yourself. Just step back — “I’m sorry to hear that” is your new best friend — until the fan gets tired of its own [blame]. Lean on your husband and dad, your allies here, and on confidence that boundaries with your family are apparently long overdue.