If you are leaving out of your will a child or person who might later contest your will and make a claim against your estate then you need to write out your reasons at length. We hold this with your will and you should keep a copy with your personal papers.
You may also wish to consider signing Enduring Powers of Attorney (EPOA). These are very useful in the unlikely event that you become incapacitated (for example a stroke can occur at any age) or ill or are overseas and needing someone to act for you. These EPOA documents can be for both property and important care/welfare decisions.
No one knows what the future holds and it can be very expensive for your family to obtain a court order to appoint a manager for your affairs. It is better that you provide for this now. For further information click on this link (“Enduring Powers of Attorney”)