You should review your circumstances with an attorney.
Most likely choices will be a Living trust/supplemental needs trust.
The answer given does not imply that an attorney-client relationship has been established and your best course of action is to have legal representation in this matter.
It is not possible to tell you exactly what your best options are, without knowing more about your situation and your objectives. Do you have a taxable estate, for federal estate tax purposes? If so, then you need to plan for that. Is this a first marriage or are there children from prior marriages? If the latter, then you may each need a trust. If the former, you may be able to have one joint trust.
You may need two separate trusts; one for your healthy kids and one for your disabled son. The trust for your son would be a special needs trust. You *may* be able to incorporate the special needs provisions into the other trust, but these documents are really very specialized, and I would think it is best to have two separate documents.
You will also want to have pour-over Wills and durable power of attorney forms for finances and medical decisions. These forms should be prepared by an estate planning attorney.
*** LEGAL DISCLAIMER I am licensed to practice law in the State of Michigan and have offices in Wayne and Ingham Counties. My practice is focused in the areas of estate planning and probate administration. I am ethically required to state that the above answer does not create an attorney/client relationship. These responses should be considered general legal education and are intended to provide general information about the question asked. Frequently, the question does not include important facts that, if known, could significantly change the answer. Information provided on this site should not be used as a substitute for competent legal advice from a licensed attorney that practices in your state. The law changes frequently and varies from state to state. If I refer to your state's laws, you should not rely on what I say; I just did a quick Internet search and found something that looked relevant that I hoped you would find helpful. You should verify and confirm any information provided with an attorney licensed in your state.
Both Mr. Pippen and Mr. Frederick raise good points. I strongly suggest that you contact a certified specialist in estate planning law. You can find a list of certified specialists in Riverside County here: http://members.calbar.ca.gov/fal/MemberSearch/AdvancedSearch?LastNameOption=b&LastName=&FirstNameOption=b&FirstName=&MiddleNameOption=b&MiddleName=&FirmNameOption=b&FirmName=&CityOption=b&City=&State=&Zip=&District=&County=RV&LegalSpecialty=06&LanguageSpoken=&x=88&y=8
The response given is not intended to create, nor does it create an ongoing duty to respond to questions. The response does not form an attorney-client relationship, nor is it intended to be anything other than the educated opinion of the author. It should not be relied upon as legal advice. The response given is based upon the limited facts provided by the person asking the question. To the extent additional or different facts exist, the response might possibly change. Attorney is licensed to practice law only in the State of California. Responses are based solely on California law unless stated otherwise.
If your son is disabled for Social Security purposes, he potentially can qualify for Medicaid and other benefits provided you do special needs planning. Typically, at a minimum, you would include a special needs trust in your estate plan. I don't know any special needs lawyers in your area but Stephen Dale, Esq. in the Bay Area [925-826-5585] is a leading CA special needs lawyer and probably could refer to to appropriate Southern California counsel. Numerous articles on special needs planning are on my website SpecialNeedsNJ.com. Lawrence Friedman, Bridgewater, NJ. Certified as an Elder Law Attorney by the ABA approved National Elder Law Foundation, former Chair NJ State Bar Association Elder and Disabilities Law Section, Member Board of Consultors of NJSBA Real Property, Trusts & Estates Law Section, Vice Chair Special Needs Law Section of National Academy of Elder Law Attorneys, and Master of Laws (L.L.M.) in Taxation from N.Y.U. School of Law.