How can one prepare for leading prayers in the mosque despite a personal lack of desire for it, and is there any blemish in the intention of taking on this role in response to a mother's request?

If you are qualified for the imamate and its conditions are met in you, then you must obey your mother, because obeying her is obligatory as long as she does not command disobedience. And obeying the mother here has benefit for her, so seek reward from Allah Almighty with the intention of obeying her and attaining the reward of the imamate.