I think it's typical of Mr Bennet's not to tell his wife anything till he has too. That way, till the last day or so he can avoid her indignant remarks about feeding a man ready to turn them out of their house, her grumblings, his daughters questions and other headaches. As for dinner, preparing a room well, that was the domestic sphere. The servants and Mrs Bennet could worry about those details while he escaped into his library!