1. Once you make the first year choice you would be a resident alien for the part of 2012 you were in the US. SInce that would make you a resident alien at the end of 2012, you and your spouse can then choose to be treated as residnet aliens for the entire year which would allow you to file jointly. Note however, that you will have to report worldwide income for the entire year, but you can use the foreign paid tax credit on form 1116 if you paid any foreign taxes on your income earned before yo came to the US.
2. Yes, you would file for an extension and then file your return once you meet the substantial presence test attaching a statement making the two choices. You can apply for ITINs with this return. You would fill out one W7 per person needing an ITIN and attach it to the front of your return and send to the address given in the instructions for form W7.
To get an ITIN (Individual Tax Identification Number) you will need to fill out form W7 and attach it to the front of your tax return. You will also need to submit additional documentation to prove your identity and status. A passport is the only stand alone document, otherwise you need to submit two documents (see instructions). You can submit original documents, however, it is safer to submit copies. These copies need to certified by the issuing agency.
Send your return, form W7 and the supporting documents to the address in the instructions (see link below).
You can also apply in person at an IRS office handling ITIN applications (see link ITIN Acceptance Agents).
Turbotax does not support form W7, but you can download it and fill it out manually (or using a pdf editor).
Write "applied for, see attached W7" in the box for the SSN/ITIN on your tax return.
Form W7:
www.irs.gov/pub/irs-pdf/fw7.pdf
Instructions for Form W7:
www.irs.gov/pub/irs-pdf/iw7.pdf
ITIN Acceptance Agents (US and international)
Acceptance Agent Program
To apply for an ITIN from abroad:
Obtaining an ITIN from Abroad
Additional publications of interest:
http://www.irs.gov/file_source/pub/irs-pdf/p1915.pdf
www.irs.gov/pub/irs-pdf/p501.pdf
www.irs.gov/pub/irs-pdf/p515.pdf
www.irs.gov/pub/irs-pdf/p519.pdf