Car seat arrangement for 3 kids

I have a 1 and 3 year old and I’m almost 6 weeks pregnant. Our mini van has two captain seats in the second row and a third row where you can have 1 seat up, 2 seats up, all up or all down.

My 3 year old is still rear facing and I’d like to keep him that way until he maxes out. However now that our car seat arrangement is changing, I may flip him forward and put him in the third row.

Any suggestions or personal recommendations on how to set up the car seats when baby comes? TIA!