You're not legally obligated to tell your children what is in your estate plan. You could leave them everything or cut them out of the will entirely. You don't have to have a conversation with them about it. They don't have to agree with your plan. What you do is entirely up to you.
But should you have that conversation? It depends on your goals. If your goal is to make things go smoothly for your heirs, it may be wise to talk about it.