3rd row suv vs booster seat

Hi 👋🏻

I am getting ready to deliver my 3rd baby. My 5 and 3 year old are sitting in the 3rd row of my pathfinder because all 3 car seats will not fit in my 2nd row. I’m starting to hate them sitting all the way back there, especially if someone hits me from behind.

My next option would be to put my 5 year old into a booster seat so I can fit all of my boys in the middle row. I definitely have had no intentions on putting him in one which is why he’s in the 3rd row. But now I’m starting to panic about which option is safer.

Any advice or options??