Hi jbrady3324.
Time travel from 2014 …welcome back to our Mattress Forum! 
Sorry for the delay in replying. Your post was put on my board by the team but slipped away when taking care some technical issues for the site.
I am seeing some good choices on your shortlist of beds for your 3 years old daughter. Generally, any mattress that uses materials that are “durable enough” (see the mattress durability guidelines here ) that you would also consider to be “safe enough” and is in a suitable firmness range for their age would generally be a suitable choice for a child. The choice between different mattresses that meet these criteria (outside of memory foam which is not a good material choice for children) would really be more of a budget and preference choice than a “better/worse” choice (see article here ). I am not seeing the common denominator in your choices aside from flippability and perhaps budget.
Based on your previous choices, MGM and QSS would be an ideal place to visit as they have a large selection of mattresses for children. You may want to have a look at Quality Sleep Shop’s Emily Mattress which is handcrafted with 1" of soft, blended latex over a firm pocketed coil and foam. My Green Mattress’s (8")Kiwi Bunk Bed hybrid mattress made with organic latex and wool batting would also make a good choice. I’d definitely pay a visit and use their decades-long experience with crafting mattresses for children to decide what is best for your 3 -years-old daughter.
In the case of a 3 years old child, the “flipability” feature may not be that important in terms of mattress durability and it is not recommended especially if you select a dual comfort version. A child is much lighter and their mattress usually does not go through much mechanical stress and given componentry that falls in the mattress durability guidelines here needing to flip the mattress for durability is not an issue. This said you may still want to choose a flippable child mattress for other considerations. For example, getting a dual comfort (one side firm the other medium) will certainly add some comfort for your daughter later when she develops more adult proportions and needs more cushiness. Also, for toddlers and preschoolers the mattress “flipability” may help offset any accidents that may happen during this age.
Arizona’s lower pricing comes from laminating 18" to 30" cut-off pieces (from Queen of Twin XL) Talalay latex cores into solid slabs. A child’s twin size 38″ wide x 74″ long will have 2-3 of such latex core strips.
Practically there is no real downside to manufacturing such a mattress as the lamination seams cannot be felt and the lamination adhesive is very strong, water-based and Greenguard Gold certified. This Kid’s all latex mattress is almost half the price of their unlaminated solid-core model which runs at $600. This mattress has the same 20 years guaranty, is as durable as its solid counterpart, and is the perfect value/quality for those with budget considerations.
4. SleepEZ Roma - sleepez.com/products/roma-latex-mattress/ is also a very good choice from one of our Trusted members Like Arizona’s solid core model, SleepEz’s Roma is made with solid latex layers which come with a higher price tag. Also, the mattress is 9" instead of 6" which would also result in an increased price point.
The mattress can be placed safely on the floor without compromising the durability and useful life of the mattress, I would still consider using some sort of Bunkie board or low-profile foundation down the road. This will also help with overall breathability, hygiene, and cleanliness. I would also consider a mattress protector of some sort.
As mentioned above a reversible mattress would help extend the use of the mattress once your daughter grows and is ready for a softer sleeping surface. If alternatively, you select one firmness only for both sides of the mattress, down the road. you can always add a topper for a little more comfort when your daughter needs it.
I’d keep in mind that especially when children are very young, they need a firm mattress that allows for free movement and a sleeping surface that is more supportive for the spine.
Older children that have transitioned to a larger mattress and are out of the crib will generally do best on a medium to the medium-firm sleeping surface. Based on the child’s stats (weight, height, and proportions) and with the caveat that children are much lighter than adults and the sleeping surface may “feel” firmer to a child than it would feel to an adult rating the same ILD latex of same thickness, here are some general guidelines.
0-1 infant …. Firm to an extra firm sleeping surface
1-3 toddler … medium-firm to a firm sleeping surface
3-5 preschooler … medium to the medium-firm sleeping surface.
5-9 school-aged … medium-firm to medium
9-12 pre-teen/tween … more preference oriented
12+ teenager … more preference oriented
Children are very adaptable and they do very well with firmer surfaces that support their epiphyseal plate and postural formation. The Signature Hybrid is a hybrid polyurethane mattress and different in many respects from all other all-latex mattresses you are considering. The 2.5" of foam on top of 8" coils would be more suitable for an adult looking for a certain surface feel. Adding to this. they have changed their specs several times over the years so if you are considering this mattress I’d make sure to find the mattress specifications you need to know so you can compare the quality of the materials and components to the mattress durability guidelines here
Looking forward to hearing about your final decision.
Phoenix