If I was in your shoes, I will wait to see the March 2013 Visa Bulletin - this will have information regarding Visa cut-offs for April and May - and this should be coming out in a couple of days. Better yet, you could give KCC a call from February 5th or so, they usually have information regarding visa cut-off numbers before it is officially released on the visa bulletin website. If you're able to confirm by early February that your number will not be current on May, 1st, I suggest you officially inform KCC of your desire to undergo CP by re-sending DS-230 and DSP-122 for you and your spouse (remember to select the US Embassy in your home country like AOS13 earlier advised).
One of the things you will need for the CP process is a Police Clearance Certificate. Start making inquiries on how to get one from the US since you and your spouse have spent a considerable number of years here. You may need to start making inquiries on how to get one from your home country too and any other applicable place you guys might have lived at.
Should your number become current in May, then I think you should still be okay to do AOS even if your current H status will be expiring on May 21st. Just make sure USCIC receives your I-485 package by May 1st, don't delay in sending it in and fingers crossed you will get an acceptance notification long before May 21st. And I also suggest you speak with a competent immigration lawyer also.
Good luck!