Up till now I've had two car seats for my child; one in DH's car, one in my mother's car for occasional trips. (I don't drive.) Just realised we very soon need to switch to another seat (hopefully one to go to age 12) but I want the flexibility of maybe taking a cab occasionally or going in a friend's car, & don't want to make my mother have another space-hogging car seat. I was looking at the Mifold booster seat but not sure how safe it is. How's best to travel with a four year old (for occasional trips)? Thanks in advance!