I didn't know what to say when a woman told me while I was pregnant with our third child, "Oh I can't have a third baby because I can't fit another one into my car". I sat there stammering in my head thinking "is this a real problem for her or an excuse?"
We had that challenge. We throw away our eldest kid's bulky booster seat. I had one infant car seat on hand--that went to the new baby. Then I measured my back seat and bought two new booster seats in the narrowest size they had at Target. Problem solved.
We don't have to curse the fact that American culture is currently so hostile to family life. We don't have to fall into mortal sin or give up on our faith There are solutions to family life that are elegant and easy and "doable". Currently, one that is working for me, is a pretty pack in play hanging out in my dining room.