that's the one i have. i recline it and sit jack in there while i make dinner or do dishes. it works fine! with the recline it doesn't matter if he has head control or not and he likes to be wherever i am....plus the ceiling fan is in there and he is mesmerized by it! LOL!
You can put newborns in the space saver, it has a recline feature. We have the same chair and she started sitting it it around 3 months. We had friends over to play games and she watched us the whole time! Now she uses it when we feed her cereal.
You can run and go put him in it right now, just make sure it is reclined. My DS sat in his when he was the age of your DS. DS really likes watching use when we are eating, it just gives him a new way to view the world.
Re: when can i put him in his high chair?
Another boy on the way!