Question Convertible car seats & Town & Country

We are ready to move our twins into the Britax Boulevard convertible car seats. We have the 2012 Chrysler Town & Country. I realized recently that the 3rd row only has one latch system & it is off centered! First off, I'm wondering if there is any way to install these 2 car seats in the 3rd row with the latch system being off centered? Secondly, if it is even possible, is it safe to have one seat installed without the latch system? I have not tried to install them yet. For now, they will both be placed in the captain chairs rear-facing, but in the future, when they are forward facing & when we have more children, they will need to be in the 3rd row. I'm trying to figure this out now because I need to know if Britax is the seat to have or if I should get the Diono Radian which has a thinner profile. Unfortunately, I had already bought the Britax before I realized the latch system issue.

Don't worry about not having LATCH! The Britax seats are a breeze to install using the seatbelts and its just as safe.
For rear facing, you could install one with LATCH and one with the seatbelt in the third row if you wanted to, or both with belts. Its very likely when your kiddos get older that they will reach the LATCH limit of the vehicle anyhow and you'll need to use belts to install. I can't remember what the limit on your particular van is but I can come back and edit this to let you know or someone else may come along with that info! The only thing is installing forward facing in the third row is tough, because you'll have only one top tether anchor. Yu want to use a top tether anchor anytime you install a seat forward facing.
As for seatbelt installs, have you browsed the manual in that section? It will show you by using a lockoff or you can lock your belts at the retractors by pulling them all the way out slowly and when they go back you will hear a racheting sound.
Another great resource, if you are more of a visual person is Britax's YouTube channel. They have all sorts of install videos.
I hope this helped to answer some questions!