Hi treehugger,
The Gemma mattress is made by Spaldin which is a Spanish manufacturer (Industrias Tobias SA is the parent company) which makes some interesting mattresses that are focused on using “safe” materials. They are very open and transparent about the materials they use and the memory foam they use has among the highest percentage of plant based polyols in the industry (which are used to replace some of the petrochemicals in the memory foam) and they are also Oeko-Tex Standard 100 class 1 certified (safe for babies) which is very unusual for a memory foam mattress. In this area they are a leader in the industry.
The “gem foam” they use in the top layer of their mattress is reticulated foam (also called fast dri foam) which is often used outdoors because of it’s ability to breath and dry quickly. There is a good description here as well.
The base layer is also a good quality 2.0 lb polyfoam.
Unfortunately the Spaldin Gemma uses rather low density/quality 3.2 lb memory foam in the top layer of the mattress which is lower than I would normally recommend for any memory foam layer more than an inch or so. The memory foam is a fairly thin layer which makes the use of lower density memory foam a little less risky in terms of durability because there is less material to soften and break down but it also means that there is less of the more costly materials in the mattress and it’s not in the best value range.
Like your own Savvy Rest mattress and several of the other members of this site … the Brooklyn Bedding total latex mattress offers a choice of layering and firmness levels which would determine its feel. If you were to use the same ILD’s in the layers then it would be very similar in “feel” to your Savvy Rest except of course the Savvy Rest is significantly more costly than similar mattresses made by other manufacturers (including some of the members of this site who make component or “choose your own layer” latex mattress).
A forum search on Brooklyn Bedding total latex mattress (you can just click this) will also bring up more information about their all latex mattress and of course there may be other members who see this and share their experience as well.
Post #2 here includes links to the better threads in the forum about mattresses and children that include information and links to some very good options.
I think that 9" of latex for younger children is probably more than is necessary and may be a bit of overkill. It may be worthwhile to consider a 6" latex mattress (either as a single layer or as two 3" layers) on the firmer side (children need firmer mattresses than adults) and then when they get older and into their pre-teens and teens then you can add a 2" or 3" topper to add some softness to the mattress when they need it.
Phoenix