Hi manazca,
I’m not sure why this would be your only choice but post #2 here includes some links to the better forum topics and posts about children and mattresses that may be helpful and include more information and links to many other options that would be a good choice for children as well.
They don’t say whether the Talalay is blended or 100% natural but either way it would be a high quality material although with only an inch of latex I would hope that the price would reflect this as well.
They don’t mention the density of the polyfoam support core (plant-based foam is just polyfoam … see post #2 here) so I can’t make any meaningful comments about the quality of this part of the mattress although it’s most likely in the 1.8 lb or higher range (I would want to confirm this) and if this is the case it would also be a reasonably good quality material that would be a suitable choice as well and there would be no obvious weak links in the mattress.
Phoenix