Hi jc,
I would never purchase any memory foam mattress that wasn’t tested and certified for chemicals and offgassing by CertiPur or Oeko-Tex or something similar … especially if they were being used by younger children who may not have fully developed immune systems. I believe SilverRest uses Chinese foams that are not certified to my knowledge and I would avoid them unless they are certified.
Some of the better quality and value (and safer) memory foam manufacturers who sell online are listed in post #12 here.
If you let me know what city you are in I may know of some good local options available to you as well.
Phoenix