Hi Sensei, thank you for replying!
We will be getting him a twin bed (have the bed frame already). He is 53 lbs, and about 4’3, average build. I contacted the manufacturer asking about their firmness, but couldn’t get any specific answers other than its firm enough for a child and somewhat softer than their crib.
After more reading, I decided that it’s probably best to go with a firm mattress now and add a topper later if needed. I also found another candidate, a futon by TFS Honest Sleep. I actually made another post asking about it (couldn’t change this post’s title to included it) could you kindly offer an opinion ?
https://forum.mattressunderground.com/t/anyone-heard-of-tfs-honest-sleep-company-and-their-futon