Say the boundary in operational terms
Name the contact, behavior, topic, access, or commitment you will and will not participate in. For a message about how to tell family you are adopting a child, use this factual base: state only the information you have permission to share and be clear about timing, privacy, and practical needs.
Define any necessary exception
If an exception is necessary, give it one purpose, one channel, and a clear limit. Ask for the conversation, support, boundary, or decision that is actually needed now. Make the immediate next step clear enough that the recipient can answer without reconstructing the entire history.
Respond to escalation safely
Do not demand celebration, explanations, medical details, or a public announcement. Use qualified medical, counseling, safeguarding, or emergency support for health concerns, coercion, or immediate risk. You do not need the other person to agree with a boundary for you to follow it consistently.