“What can you do legally ahead of time to make a period of incapacity easier on your family”?
The most important thing you can do is sign a well-thought out power of attorney, tailored for your situation.
Once you have a well-designed “Medicaid-sensitive” power of attorney, another legal document you should consider, if you are married, is a Testamentary Special Needs Trust.
While you are alive, you can add a special needs trust for your spouse to your will. Then if your spouse needs Medicaid after you die, the assets in the trust will be there to take care of your spouse, but will not disqualify your spouse from receiving Medicaid.
While you are thinking clearly and able to do good, thoughtful planning, you should review whether a testamentary special needs trust is the right strategy for you.
(The above should not be construed as specific legal advice and is intended for general information purposes only)