Get your hubby to talk to your mil that she can go ahead to consult the fengshui master for the name. But both of you have the final decision for the baby name. Else u can let your mil know what name you have chosen for the baby and let the fengshui master see if is suitable for the baby anot. I also dont believe on fengshui but for the sake of the baby i will consult fengshui master for a name based on the birth date/time when he is born. Anyways the birth certificate dont have to be done during your hospital stay can do after that so dont worry so much.
Yes don’t have to do at the hospital. My husband registered through lifesg app plus they give you time to register . But if your mil persists you guys can go ahead register the name you want and let your mil call your child by the name she wants. At the end of the it’s the parents decision tho.