Axkid - ONE 2 Reha

You would want to have your kid rearward facing for as long as possible. If you dont want to take my word for it, go to Youtube to see car seat crash tests, it becomes very clear why forward facing just isnt safe for smaller kids. And specially since your kid is a big one, I would advice you not to buy a "toddler seat" but one that goes to about 6 years of age on average.  If you want one with isofix the pick is Axkid One. It has adjustable leg room and slide, both of which can be adjusted after installation. Its super safe, passed the most strict car seat safety test ever (Swedish Plus-test).  Another long lasting Plus-tested rearward facing option, but without isofix, would be Besafe Stretch, Britax Max Safe Pro or Axkid Minikid.  These are not the cheapest ones but the again if the seat can be used for several years and makes your kid travel significantly safer, I would call it worth it. Sometimes I wonder what goes in the mind of people who spend thousands or tens of thousands on a car so its as safe as possible but then pick a lousy forward facing supermarket booster seat for their small kid who WILL break his neck in it if the accident ever happens. 

Axkid one two or one three

It’s not until 12. Most car seats have a height or weight limit, not age, so will really depend on what centiles your baby is on as to how long the seat will last you. Axkid one two is an extended rear facing seat that should last most children until 6 or 7 years. It also have a very good safety profile and is Swedish plus tested.