Hello,
My father has recently passed and we would like to have "May eternal rest be upon them" in Irish Gaelic on the headstone. I don't trust online translation tools, so wondering if this is a correct translation? “Go Raibh Suaimhneas Síoraí Orthu"

Thank you,
Heather

That looks alright to me.

Thank you!

Alternative:
Suaimhneas síoraí dóibh

But "Go raibh ..." would not be used as the complete form here, rather: "Go dtuga Dia ..." (May God give ...) or Go dtugtar ... (May he be given ...)


BTW: Why "them"? Are other persons involved?
If not: dó "for him" instead of dóibh (or air "on him" instead of orthu)

My mother will be sharing the headstone, so that's the reason for "them". Thank you for your reply!