Calculate the days you have stayed in Canada so far. If you have not been outside Canada for more than 1095 days since you got your PR, you are still ok. If you have, then you have already lost your PR.
The good news is that immigration probably doesn't know that yet. If you go back to Canada now and they don't catch you at the border suspecting you of not having lived in Canada enough, then you can save your PR. What you would have to do is arrange all the things you need a PR card for, SIN if you didn't already get one, health care, drivers license etc. before the PR card expires and then let it expire and not leave Canada and not apply for a PR card renewal until you have at least 730 days in Canada in the last 5 years and can prove it. Immigration regulations forbid immigration to question your status while you are in Canada unless you apply to renew so as long as you don't leave and don't try to renew, you are safe and in 2 years, your status will be good again and you can get a new PR card.
You can bring your cars and household items but you do need to make a list of everything you have with you and it's approximate value as per if you were to sell it at a garage sale. Include serial numbers on everything that has one. If your cars are leased, you will have problems bringing them because it's unlikely that the leasing company will allow you to import them to Canada since they will have a hard time billing you there.
As imigrate said, there is no sponsorship for citizenship. If you had lost your PR, your eldest son whether he is a PR or a citizen, could sponsor you for PR as well as the younger brothers but he would need to be making around $45,000 a year and it would take years.
Thanks Immigrate and Leon for your detailed responses. Assuming I enter Canada now then how can I take my household items including cars? I will be entering as if I was out for few days. If I take these items now will they not question my status then?? Two of my cars are paid off. If I enter in May or June 2010 how soon can I apply for DL's and Health Card(Our PR cards will be expiring in 2nd July 2010) ? We all have our SIN #s and our cards with us.
I thank you all in advance in anticipating your response.