Unlike in Europe there is no ISOFIX system in the USA.
We recommend the Liberty Lodge for families travelling with small children. It has two three point seat belts at the back seats, but no top tether.
In the Family Freedom you have two waist seat belts in the back as well as two top tether. It is 21'' (53cm) wide.
The Couple Condo has no proper back seats (only a bench facing sideways with waist seatbelts). Thus we recommend it only for two travelers.
In the Horizon Hopper you have one regular and one waist seat belt in the back but no top tether.
Note: If you are planning to bring two child seats, keep in mind that the outer one might not be completely secured.
Do not put a forward-facing child seat in the front, unless there is no other choice. If you must do so, make sure the car seat is as far back as possible, the child seat is securely fitted and the child is securely held by the seat belt or child seat harness, keeping the child as far as possible from the dashboard.
In addition to conventional child seats with a back section, there are also so-called booster seats without a back section.
These are only permitted from a weight of at least 22 kg or a minimum height of 1.25 m !
Of course, you can also bring your own child seat, just make sure it fits the dimensions of the rear seat!
If you are travelling to Europe, check this article.