It is easy to check the GRO index for birth registrations of possible children following marriages which makes it easier to track them down on the following census. As I mentioned they were registering births
DIXON, JAMES mmn MOLYNEUX
GRO Reference: 1877 S Quarter in PRESCOT Volume 08B Page 708
In 1881 that family are at
RG11
Piece 3731
Folio 34
Page 9