First of all, the elderly at home should not interfere too much with the naming of children. Parents should have absolute control over their children's names, and grandparents can provide some advice and help. After all, the child is a piece of meat that falls from the mother's body, and it is the mother's baby. Therefore, the mother should participate in the naming process.
Secondly, if you want to refuse your in-laws to name your child, you can tell the other party that you have already named the child, or you can directly refuse the other party, so that the other party knows that you don't want the other party to name it. If your in-laws insist, you can register your child in advance and let all the dust settle in advance. However, if the in-laws relent, they should try to politely refuse to avoid hurting their hearts.
In short, when naming children, the elderly at home should not interfere too much. If you want to refuse the parents-in-law to name their children, you should try your best to be tactful. If it is really irreconcilable, you can choose lottery and other methods.