Sorry but not sure why you think that her chairites weren't far from her mind when she was having George? I think it is a good idea to ask for donations to charities, rather than gifts as they are liable to get plenty of gifts for themselves and the children.. but that could just be PR on teh part of the Cambridges. I mus admit to not being a great Kate fan and feeling that in her "girlfriend" days living with Will, if she'd been inclined towards charity work, she could have done something quietly with say a detective in tow, before she got intot the royal round of engagements.
But their public engagements are another matter and I think that Charles and the queen are happy with the way things are, with W, Kate and Harry all not doing a lot of royal work, as yet, and gradually taking on more. Partly for financial reasons and partly for reasons of "status".. that HE, Charles is heir to the throne and will be king some time in the foreseeable future adn the queen wants him to be the focus rathter tahn William and K.