Hi lglawhon,
Thanks for taking the time to share your comments and feedback.
I would be a little bit cautious because a mattress that would be soft enough for many adult’s preferences will often be too soft for a child. In many cases what they may “like” best may also not be what they “need” (just like food choices).
Having said that … if your son has grown larger and is getting closer to more adult proportions and a firmer mattress that would be suitable for a younger child that needs a firmer mattress isn’t quite soft enough for him then it would generally be OK to add a topper with another inch or two of latex to provide some additional softness and pressure relief as long as it’s not any thicker and not too soft (I would probably look at an ILD in the range of the lower 20’s or firmer).
Some of the better online sources I’m aware of for latex toppers are listed in post #2 here.
Phoenix