Clek - Fllo Convertible Car Seat

If you want good three across seats, without flame retardants, Clek Fllo and Foonf both come in a couple of totally flame retardant free fabric options. I have Mammoth Fllos for my twins and they are great. They do extended rear facing until 40lbs (in Canada) or 50lbs (in USA) iirc, which is a really important safety feature - you don’t want to turn them around too early. If you want to only do two seats, the only seat I can think of that wouldn’t drive me nuts are the Britax clicktight seats - some of which are flame retardant free - but I don’t know if you could find one that would still do three across. The click tight seats are really fast to install securely, I had a Harness-to-Booster one for my oldest child when they outgrew the Clek Fllo but weren’t ready for a booster (95%ile kids are a car seat challenge) and I had no qualms uninstalling and reinstalling that seat whenever I needed to.