Sorry in advance for yet another car seat thread. From January I am childminding my nephew and have had Mothercare fit child seats for DD (3yo, 96cm, 16kg), DS (1yo, 25kg) and my nephew (1yo, 21kg) they all need to travel regularly in the back of my Honda CRV.
Currently I have DS in his rear facing Britax Isofix infant carrier which will last him another couple of months and DD in a Maxi Cosi Priorifix (also Isofix) which should in theory last her until 4yo but she is starting to grow off the top of it - her head is no longer wholey contained within the side impact part of the seat iykwim. She is nearly 16kg and 96cm tall.
When my nephew is with us from Jan DD will travel in a high back booster seat which was fitted by Mothercare and she was checked by them for height/weight etc. They assured me she was safe to travel in it. I wanted a 1-2-3 seat but because of DD's weight they said not to buy one as she would outgrow the 5 point harness too quickly and would be left just with a basic booster at about 4/5yo which is too young. My nephew will travel in DD's Priorifix.
However, I don't really feel like DD is mature enough to be without a 5 point harness even if she is big enough. What do you think? And does anyone know of a 5 point harness seat that goes beyond 18kg?