I can recommend foam mattresses, they are generally firmer than innerspring. Foam beds have a longer life span, as the coils can lose their bounce. Futons a long lifespan, can easily be restuffed, and are very low maintenance, making them a great choice too. They are also firmer, offering great support for a young child’s growth and sleep. Here you can find the best variants https://sleepmentor.net/best-memory-foam-mattress/.