There are several issues here.
If you are married, filing single is never an option.
I am assuming 2017 was your third year in the US. In that case you would indeed meet the substantial presence test and be a resident alien. And I am assuming your spouse is a resident alien too.
As resident aliens, you and your spouse are required to report worldwide income for the ENTIRE year, including income earned after you left the US.
If you file as resident alien, your best option would be to file jointly, but you would need to apply for an ITIN for your spouse.
You both can apply for an early residency termination date (if your spouse had no income the entire year, she would not need to do that). That would make you a dual satus alien. You would then file a dual status return as married filing separately. Turbotax does not support dual status returns.
You can claim your children on either the resident alien return or the dual status return, but you would have to apply for ITINs for your children. No way around it.
You can simulate your return by entering "dummy" ITINs for anyone without an ITIN/SSN. ITINS start with a 9, so for example, use 99-999-9999 for one, 99-999-9998 for the other child. The 2017 software isn't available yet.
And yes, you would have to convert income not in USD to USD, either using the exchange rate of the dates you received the income or a yearly average (the IRS publishes yearly average rates for the previous year each year).
