My heart goies out to you for the loss of your son. Thank you so much for your video. It is such an important message and such an important thing that you are doing, especially helping people who can't afford it keep their children in a 5-pt harness. I have a 3-1/2 year old and I 6 mo. old. My 6 mo. old is 2 lbs. away from growing out of his infant car seat, and I am going to give him my 3-year-old's Britax Marathon (it goes up to 65 lbs. and has a 5-pt. harness), which we bought when she grew out of her infant seat.
Luckily, last week I asked their pediatrician what he recommended for my daughter: buy her a bigger car-seat, or put her in a booster. He told me to definitely keep her in a 5-pt. harness as long as possible, and to keep her in her car seat and buy another one for my son, or buy her a bigger one, such as the one that you suggested. I'm so glad that he told me that, and that your video is also getting the message across to people who may not ask their doctor. Thanks so much for doing what you are doing.