Hi newkidontheblock,
Post #2 here includes links to most of the better forum threads about children and mattresses including links to some very good quality/value options.
Both SleepEz and Arizona Premium are members here which means I believe they compete well with the best in the industry and would certainly make a great choice. If you are looking at a latex mattress though for your child though … I would lean towards a 6" mattress in the medium/firm range (28 ILD is probably the lowest I would generally consider) with either one or two layers and leave off the softer comfort layer until they are older and their bodies begin to mature.
This type of mattress will easily last more more than 10 years (either by itself or with a topper).
Phoenix