If it was me in your position I would tell them both to get out of my life & mind their own business. You are divorced from your ex & his new partner has no right to be involved in your life choices.
As far as I'm concerned the only problem with the name is with the new resident! Absolutely fed up with these cry baby people who try to change anything that upsets their sensitivities. We have historical values to preserve & if modern day yuppies or aboriginals are offended, so be it.