We've done three kid seats in an 06 YXL Denali with captain chairs. There was no way either my wife or I could have reached into the middle of a bench seat to remove the baby without messing up our back. It sounds nice to have all three in the 2nd row but there's also a proximity factor if one gets sick (use your imagination here).
Our 08 YXL Denali had the 2nd row bench. It was great because one kid actually preferred the third row because he turned it into a couch. I can attest though, there's no way the wifey or I could have managed a row of three car seats in one row. We had a stroller that allowed one car seat to clip in and the other seat was for a toddler. That worked well because we could pull the car seat on one side and flip the seat forward with the base attached.
With the seat flipped forward and base attached we had access on our knees to the other two kids. I'd find a GM truck that has a bench seat at a dealer and bring all three seats (without the kids) and literally check it out.