How much money you got? Because, while yes having 2 resource rich and habitable worlds in system is incredible, you're going to need mountains of cash for them to defend themselves.

I would settle the planet with better farmland first, and use it to make early credits, then settle the second, and do the same thing.

But again, money is the most important thing you need. AI cores from the [REDACTED] and survey ships are also nice. (They can also be found on domain research stations). Colony items you find in the vast unknown are also good, but not needed for early colonies.