3 across in a rental

I have 7 kids so I usually drive big vehicles and I'm not worried about how much room the carseats take up. But my sister and I are going to our uncle's funeral (last minute, obviously) and need to rent a car with 3 children between us.
We are taking 8 month old 15 pound rf baby, 22 month 25 pound rf baby, 5 yo 39 pound usually rf due to having Down Syndrome.
We have the following carseats available between us
graco my ride 65
graco contender
britax marathon classic
britax roundabout 50
(those are both quite old, but they are not expired and have been stored in the house)
Graco Turbobooster (I think it's ff only) but 5 pt harness
britax pavilion 70-g3

Will any of these fit 3 across? What size car?
What would you do?

The Britax Marathon Classic expired last summer at the latest. The Roundabout 50 at the same time. They have six year expirations. The date they were made is on the sticker at the child's left shoulder.

A Turbobooster has no harness. Do you have a Nautilus?

Is the five year old 39 pounds naked or fully dressed with shoes on? All of your seats go to 40 pounds rear facing (except the expired Britaxes, which go to 35, or 33 if they're quite old), so if it's 39 pounds naked they'll need to be forward facing. Great job keeping them rear facing this long, though!

The my Ride is quite wide, as is the Pavilion, but you don't have a plethora of narrow seats. In fact, you have none.

But the older Britaxes aren't an option. If it's a Nautilus that doesn't play well with others. So that leaves the My Ride, Contender, and Pavilion as the only potential options in a three across, and they're not great. A full size vehicle would be your best bet, or see if a minivan or three row SUV is cheaper. Or two cars.

Edit: If you got your Britaxes at Target, they may still have a couple of years, I'm remembering Target did that until 2012. Everywhere else they went away in 2010. They don't get you a lot of options for narrowness, though.
Wendy

Could you acquire any new seats?

The MyRide is wide, but sits up on a super narrow base, so other seats can often puzzle under it. It also is very reclined forward facing, so if the main issue for the 5 year old is low tone, it's a good one to use forward facing.

A pair of Scenera NEXTs might puzzle well with the MyRide in the center, especially if the center seat has a hump that raises up the MyRide. The Scenera NEXT can be installed as upright as you want when rear facing, as long as the child can sit unassisted, which might make it easier to make the puzzling work.

Another slightly more expensive option is a pair of Safety 1st Guide 65s. They are definitely good for puzzling with a MyRide.

And finally, if there are compelling reasons to keep the 5 year old rear facing, you could get a Diono Radian RXT or R120. If you can get a good rear facing install with it in the center (which is a big if--any weirdness with hinges make it not work) the MyRide and Contender should both puzzle well with it.