Indeed, they don't need a carriage...
Written by Thérèse
(3/16/2013 5:49 p.m.)
in consequence of the missive, Mr Knightley has his own carriage, penned by Margaret C
... of their own, as there is Mr Woodhouse's and they cannot afford going far while he is alive.
One can suppose that Mr Knightley will continue riding to town when he has to go there — and go less often, or come back quicker in spite of his brother, sister in law and nephews whom he loves.
And for their honeymoon, I suppose Mr and Mrs Knightley travelled in Mr Knightley's carriage, with the Crown's post horses.