Their stay is till July 23, 2012.. My father has been dignosed with stage 4 pancreatic cancer and will be undergoing chemotherapy. They both are Singapore citizens.
Yes, since your parents are immediate relatives, you should be able to adjust their status. I had a client who is an American citizen who adjusted the status of her Austrian mother last month. She entered the U.S. under the Visa Waiver Program. You should consult with an experienced immigration attorney like me or someone else to help you with this application. Do not try to file it on your own.
As a U.S. Citizen, you must be 21 years of age to petition for your parents.
You should also check the I-864 Affidavit of Support requirements. If you do not qualify, you will need to find a co-sponsor.
I always recommend consulting with an experienced Immigration Attorney to make the process as easy as possible. You should also review all information available at www.uscis.gov.