Do you mean this type of Mandala?
http://www.mandalaproject.org/Its the first link about Mandala's and Children but I didn't read it, I'm not familiar with the concept or anything...based on the top few paragraphs of
thispage within the site, I'd say that Mandala is a spiritual/philisophical concept. Probably better studied by the parent, who could then apply such concepts in their everyday life with the child, not so much as TEACHING the child, the philosophy, but living it by example...
I don't like to feel like I'm underestimating children, especially babies, but I do feel that there are some things they can't learn without context...For example, I have a hard time seeing how a baby can learn to speak a language from a textbook, even if they can read. I think they'd at least need to be 2 or 3, because then they might work examples, verbally and such and even then, for them to hear and understand the language just from a textbook, that would be some level of uncommon genius, at least thats my thoughts on the matter. I think a philosophy and concept of spirituality is beyond a child to really UNDERSTAND, they can learn it rote, but they wouldn't understand it until they gain experience living it, seeing mom and dad living it, etc...
Which is why many children ask so many questions about religion and God. Spirituality is something that one must develop throughout their life, you might have a leaning/knack for it, but its hard to understand religion without world experience, I think...