> if a user changes a checkbox, the checkbox state must be set to all the children of this node.
This is what the CheckChildren functionality does. Note that checked state of items that are not loaded is not set, because the items are not available on the client side.
> Is it possible to expand all sub nodes (complete structure) of a given node when loaded on demand?
Yes, and this will solve the problem with the not-yet-loaded items above. See the linked Dojo snippet on how to load all subnodes on item check
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