Third baby car logistics

I just found out that I’m pregnant with my third! I have a Honda Pilot with three rows and a removable middle seat in the second row.

When this baby is born, my kids will be a little over 2.5 and 4.5. I have the option to try and fit 3 across in the second row and get slimmer car seats, or remove the middle seat and have the oldest in one of the third row seats and the two youngest in the second row. My only issue is that I’m not sure how I would get my oldest buckled in if she’s back there. Can a 4.5 year old buckle themselves into a carseat?