I agree, walk first down to Pier Head for photos etc at the Fab Four Statues. Then hubby walks through Albert Dock (with the river on his RH side) to the start of Magical Mystery Tour.
(On that walk through Albert Dock, look out for the statue of Billy Fury, Liverpool pop idol a bit before Beatles-era).
IMO you other two should walk with him 'most' of the way; Albert Dock area is interesting and has many shops in it. Then you two turn L into the main shopping area of Liverpool One. (Much better than retracing steps). I've enjoyed a Costa Coffee shop, for sit down, drink / snack on that route in Albert Dock area a couple of mins before MM Tour.
Slight digression - for your awareness as you are from Canada -
Just before your reach Liver Building, look out for the Maple Trees as you cross Canada Boulevard. All explained in my post #8 in the link below. Your walk will take you very close to all the items indicated (if you fancy visiting them, instead of shopping that can be done in any city).
https://www.tripadvisor.co.uk/ShowTopic-g186337-i414-k14808298-Recommendation_for_Unique_Pubs_Restaurants_Bars-Liverpool_Merseyside_England.html#121144706