Hi ciuvak,
They are both similar materials but I would give a slight edge to 100% natural Dunlop yes (see post #2 here).
For a child I would also ask Ken about a 6" 100% natural Dunlop mattress and then wait till they were older to add any softer latex on top as a topper (or you could purchase a thicker cover and use the core and the topper inside the new cover).
Kids won’t need the extra 2" of soft latex.
I don’t recommend specific mattresses (just help the members here identify weak links, eliminate their worst options, and help connect them to better retailers and manufacturers) so they can make final choices based on their own personal value equation but post #2 here includes links to most of the better forum threads about mattresses and children which includes links to many options that would be good choices for children. If you have already decided on a latex mattress then post #21 here has a list of the members of the site that sell latex mattresses online in a wide range of designs and styles.
There is also a list of online sources that ship either from or to Canada in post #21 here.
Arizona Premium is certainly one of the “value leaders”.
Phoenix