Where does help become undue influence?
Trusts fall into one of two main categories. The first category is composed of those that are established while the grantor (one who establishes the trust) is alive and are termed inter vivos (while living) trusts.
Your obligations to your family or loved ones do not stop, even if you have already passed on. If your family, especially your children, are still heavily dependent on you, you can still provide for them through proper estate planning, even if you are no longer present.
The key to avoiding bitter conflict among heirs, is to have candid discussions well before the reading of the will.