I am having another baby in a few weeks and the logistics of who will look after DS and where he will go are very dependent on lots of variables. My DH cannot drive so we may need to drop DS off in taxi somewhere on way to hospital or get him picked up by someone who doesn't have an appropriate car seat for him. I know legally children can travel in taxis if there is no car seat or in cars in extenuating circumsatances. However, I would like him to be as safe as possible and I was wondering if a booster seat and one of those seat belt adjusters would be safer than nothing, or not? He is 3.5 and quite tall but also quite skinny.