At 18 days old, your lo is still adjusting to the outside world. I would not worry too much about a routine at the moment. You can start to try to implement EASY at this age, but it would be more E, nappy change and then S.
With regards to going out running errands, it is probably better to try and do these during nap times, so that your lo can sleep while you are out.
HTH's
Paula