Hi Leosmum!

That's a long way to fly solo with a 20 month old!

I would go with the Sit and Stroll. One part of the equation for me would be all those airports that you'll be going through. With the Sit and Stroll, your son will be in a stroller as you move through the various airports; with the CARES + portable stroller, you'll have to either be resigned to holding his hand through the airports (a scenario that would give me the shivers with a rambunctious boy toddler!) or cross your fingers that no one makes you check your stroller for any of your segments (I have had mixed success with carry-on strollers, even on planes where there was room and the posted policies on the web have said collapsible strollers can come on the plane as carry-on luggage).

The core downside with the Sit and Stroll is the lack of carrying space under the seat. That can be rectified if you have a backpack or other bag that can hang from the handle of the Sit and Stroll.

You could also plan on checking your stroller at your departure airport, and picking it up with other luggage when you arrive at your destination.

Good luck in your travels!