[Papooses]

This the luxury version of the Toyota Highlander, right? If so, I don't believe this is possible even with the narrowest of infant seats ... which would need to be replaced with convertible seats within a few months anyway -- I could be wrong, but it wasn't possible in my parents' Highlander Here's the measurements page anyway (Cosco Arriva is not available to the general public)

Does your 8 year old pass the 5 Step Test in the middle row center position? If not you'll need a booster -- backless is fine in the center or outboard so long as you have rear side curtain airbags, but a highback booster would be safer in side impacts withut the rear curtain airbags. Boosters can be easily moved out of the way. I would have 1 baby behind driver, then let either older kiddo climb into the back, then click the other baby into carseat base on the other 3rd row seat, then let other big kiddo into the middle row.

I haven't been inside this specific vehicle, though & I wonder if the vehicle manual allow carseat installation in the 3rd row? Or are you willing to let the older kids climb into the back from the trunk/cargo area if necessary

	Convertible Car Seats Convertible seats are for infants and toddlers. The seat can be used as a rear-facing seats for younger children, and switched to a forward-facing seat on the child's first birthday if the child weighs at least 20 pounds. However, experts recommend keeping the child in a rear-facing position until he or she outgrows the weight or height allowed by the safety seat.

	Booster Seat A booster seat raises your child up so that the car's lap and shoulder belts fit correctly. The lap belt should fall across the upper thighs. The shoulder belt should go across the middle of the shoulder and chest. A booster seat is used for older children up to about 80 pounds. Some states have passed laws requiring booster seats for children up to age 8 or 80 pounds. Check your state's law.

	Graco CarGo booster seat - Click for more info The Graco CarGo is a dependable and easy to use booster seat. When your child is on the lower end of the height/weight limits for the seat, the 5-point harness is used to keep them safely in place. It features a convenient one-pull snugging mechanism in the front of the seat - making it easy to tighten the straps down after your child has been buckled in. When your child is around 35-40" tall, the CarGo's harness can be removed, so that the seat can be used as a belt-positioning booster, using the vehicle's lap and shoulder belt. In this mode, the Graco CarGo will work for kids up to 54" or 100 lbs. Both the Platinum and the Ultra CarGo feature an Energy Absorbing Foam (EPS) liner, a removable, washable seat pad, and a cup holder. The Platinum CarGo is a softer and more comfortable seat than the Ultra CarGo (although still not as comfy as the well-padded Britax booster seats).