How to complete my tax return with a spouse and child who do not have SSN?

I am a bit confused as to how I should be filing my taxes and need a bit of help. Online tax services like Tax Act and Turbo Tax require SSN for my Canadian spouse and child (which I do not have at the moment).

  • I am a US citizen born and raised
  • I have a Canadian spouse who is born and raised in Canada (currently going through process to get a green card)
  • We have a child (already have birth certificate and waiting on SSN in the next few months)
  • I am currently staying with my spouse and child in Canada as a visitor (I am not a legal resident. The only thing I have that allows me to stay here is a Canadian visitor visa)
  • I have been staying in Canada since early 2016
  • I still work remotely for a US based company
  • I still maintain a legal residence in the US
  • I have been claiming higher withholding allowance for both Fed and State

My questions are:

  1. Should I file married jointly, married separately, or single?
  2. If I should file separately now, should I file an amendment at some point down the road and file as jointly once I receive their SSN?
  3. Can I still file correctly even if they both don't yet have their SSN?
  4. Should I file an extension to give me time to receive their SSN and then file?

I'll be happy to clarify any questions.