Thanks for the reply, that was helpful. I still have a few doubts:
1 - Regarding myself and my wife, and if I understood you correctly, we can 1) file separate returns where I file a dual status return and she files as nonresident, or we can 2) choose to be treated as residents and file a joint return. In the later case we'll be taxed on worldwide income for the entire 2015, but I believe I will be able to claim a foreign tax credit for the income tax I already paid in Portugal for 2015 income, to avoid double taxation. Is this correct? Which of these 2 options would generally more advantageous for us?
2 - Regarding my children, where you say "If they will become resident aliens in 2015", do you mean 2016? By my calculations, my children will only meet the SPT by May 15 2016, but by then I guess I will already have had to file my tax return, so I don't understand the timing - how will I be able to claim them as dependents and claim the child tax credit if by the time I have to submit my tax return they didn't yet meet the SPT? I read something about Form 4868 in Pub 519, but it is not entirely clear to me. Does it mean I can delay my tax return until my children meet the SPT so I can make the first year choice for them for 2015 and then treat them as dependents for 2015?
3 - When will I be able to claim allowances for my children on my form W-4? Only when they meet the SPT in 2016?
Thanks for your help.
