Hi Lroth1986,
The post I linked in my last reply about children and mattresses includes more information and sources for other options that are available and would work well for children that would be in a similar budget range (or in some cases lower). The tutorial post also includes this link to a list of the members here that sell online and many of these also make latex mattresses that use different types and blends of latex with a wide range of features, options and price ranges that would also be worth considering. Posts #3 and #4 here also include some lower budget latex and latex hybrid options that may be worth considering as well.
No … I meant that children usually do better with a firmer sleeping surface because they have less “curvy” bodies and because their spine is more flexible but that with latex a softer layer is a little less risky than it would be with other types of foam (such as polyfoam) because latex has a higher compression modulus which means that it gets firmer faster with deeper compression than other materials. In general terms though I would lean towards a medium firmness sleeping surface for children rather than a soft and then add a softer layer as a topper down the road if and when they need it.
The foundation post here has more information about the types of support systems that generally work best for different types of mattresses and includes some good sources as well.
Phoenix