Hi jeffcwheeler,
Welcome to the Mattress Forum! 
The new 8" version of the Arctic Dreams mattress is a medium firm/firm product, and would be suitable for a young child, in terms of overall firmness and quality of foams. Children tend to gravitate toward softer mattresses because children have a smaller mass and softer beds feel “cuddly”, but a medium firm/firm mattress is a more recommended surface comfort. Dreamfoam is a member of this site which means that I think very highly of them.
If you’re interested in more detail, there is more information in post #2 here about mattresses for children. There are many links describing “safe” materials including a link to some additional comments and some general firmness guidelines for children in post #2 here. It’s quite a bit of information but it covers everything you would want to know about your question.
Phoenix