The choice of your executor is probably the most important decision you will make when you do your will. Your executor will be responsible for burying you, for selling all of your stuff and collecting the cash, for communicating with beneficiaries, and for distributing your estate. They will navigate tax issues with CRA, be a peacemaker among beneficiaries who may have conflicting requests, and will generally be the person who most determines how much is left in your estate at the end of the day. This is not a decision to be made lightly.
Often, people default to an executor. They will choose a child, or maybe all of their children; I once had a client name all six children jointly. However, this can backfire in a major way if you are choosing because you’re “supposed to” choose your child, instead of choosing mindfully.
If your child is a responsible adult who can manage all of the emotional, mental and physical labour of administering an estate, then by all means choose that child. If not, don’t be afraid of naming a friend, an advisor (if permitted – many professionals are not allowed to be executors for their clients), or a bank.