I have come across John Wallace ORCHARD. I cannot say for sure, but he may not even be a part of the particular ORCHARD family I am tracing as I have not been able to 'link' him to anyone (same goes for your Mary Ann ORCHARD). I had been told that there was at least one other ORCHARD family in roughly the same area and that they weren't related to my husband's ORCHARD's.
It appears at present that all 'my' ORCHARD's that planned on immigrating to N.Z had already done so by the end of the 1850's (over a period of 6 years from 1850-1856), and that there's nothing to show so far that any other members of the family made the voyage at later dates. But, I do still have branches of the family yet to look into in the U.K.
If you have anything on John Wallace's parentage, then I'd be interested in knowing more, as that may provide some clues as to which ORCHARD family he may belong.