We don't do a lot of journeys with ds but have got a couple of big ones coming up as we travel for Christmas. He is using his cousin's car seat, but I have recently learned this expired 6 months ago. Unfortunately at 14.5kg and only 96 cm, even though he is 4 years old he can't go into a high back booster. My options are to leave him in the seat until he hits 15kg/100cm then get a hbb ( this could take 6 months or more), buy a new extended rear facing seat that goes to 25kg or buy a forward facing harness seat that turns into a hbb at the right size.
Which would you say is safest to do between leaving him in his current rear facing seat or moving to forward facing harnessed seat? Has anyone else continued using their seats for subsequent children when the seat is older than 7 years? My other arguement is which is most reasonable between us buying an expensive new rear facing seat or one of the other two options which are cheaper and last longer? We won't be having any more children so won't need any seats after he's finished with them.