Since are getting mixed advice, (presumably from non-lawyers,) the best thing for you to do is consult with a probate attorney who will be able to review all facts and advise you accordingly.
I agree with my colleague that you should seek advice from a probate attorney in your area. A "conservator" generally means a person appointed by the court to administer the property of a disabled adult, while a "guardian" is a person appointed by the court to make decisions regarding "the person" of a disabled adult. Under the Guardians for Disabled Adults section of the Illinois Probate Act, if your son is disabled and totally without capacity, if it is in his best interests the court can appoint a “plenary” guardian who would make decisions about both his property and his person.
***Please be sure to mark if you find the answer "helpful" or a "best" answer. Thank you! I hope this helps. LEGAL DISCLAIMER I am licensed to practice law in the State of Illinois and have an office in Kane County. 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. I hope you this answer helpful.
Hi, Good for you thinking ahead to plan for son's approaching birthday. The answer to your question will likely depend on where he resides. If he resides in Illinois, you will be seeking to have a guardian appointed of his person, his estate or both. You should seek to hire an attorney who is knowledgeable about both guardianship and estate planning, so you can also begin to plan for your son's special needs in the future. You can search for attorneys by practice area and location here on Avvo.com. Look for someone who resides in the county where you son lives. Be encouraged.
Of course, as always this answer is general in nature, applies only to Illinois law, assumes certain facts omitted from the question and does not take into account any facts specific to any person’s particular circumstances. No attorney/client relation is created hereunder and I highly recommend you seek first the counsel and advice of an experienced contested civil litigator prior to taking any actions relating to this matter, as seemingly insignificant actions may have unintended consequences.