I'm not sure how convenient it'll be to carry your kid in and drop them in yourself before strapping them in but once they can get in the car themselves you can have them make their own way into the rear facing seat and then you just reach over and strap them in
Oh wow, I haven't even thought about the little fella climbing in himself. I actually think he'll be able to do that soon. He can get on and off the sofa now. That will be a game changer!