Just found this as I've an interest in the canal boatmen. You might get some more help on the Lancashire boards!
Anyway...one thing it might be helpful to know is that the boatmen who worked the Leeds-Liverpool usually only worked that canal. It was built wider than most canals and most of the boats that worked it were barges, not narrow boats. So in general, that would mean that any children still being born on board would be born in places along the route - though most families were land based by the late 19th C.
Have you also looked at boatfamilies.org.uk for help? I couldn't find the names you mention but there may be other names which ring a bell.
Bit more I've found that backs up some info elzabels has given...
From the 1911 census there's a Sarah and Charles Campion living on Bengal St, Chorley, with one child. Sarah is born in Appley Bridge (which the canal runs through). Looking at Lan-opc (a free site), there's a baptism of Sarah Elizabeth Johnson 1892, Christ Church Liverpool - parents Jonathan and Elizabeth, abode Wrightington, occupation Boatman. That suggests the family had a house in Wrightington/Appley Bridge or thereabouts (going into Liverpool for hatchings and matchings was common as the boat families met up there - confused me when I first found these in my own family!), Can't see any other Johnson baptisms that fit though.
I've also found Jonathan Johnson (born Stockton Heath) on the 1891 census with wife Elizabeth and children Joseph and Mary E, born Appley Bridge and Standish (both on the same stretch of the canal). He is listed as Master of a barge (this is important), and resident on that day at Armley - the Yorkshire terminus of the canal. The family are obviously travelling with him. The barge seems to be called "Alice". His wife is born in Wigan so maybe this marriage would fit: Jonathan Johnson & Elizabeth Aspinall, 1887, St Catharine, Wigan (from the free Lancs BMD site).
One more edit - found Elizabeth Johnson in 1911, aged 44 as a Patient in Prestwich, listed as married and 'worker on barge'.