They should plan to move when the immigrant visas are issued, because admission on those visas begins conditional residence and its residence expectation. Filing the petition does not require moving; receiving the visa effectively does.
The move date is set by the visa, not by the wire
The petition can be filed from Guelph/Eramosa once the capital is invested or committed and the source of funds is documented. Nothing about the filing requires the family to be in the United States, and adjustment of status from inside the country is available only to people already there in a lawful status; a family living in Canada will process through the consulate. Processing times for the investor petition and then consular scheduling are long and vary; check current USCIS and consular figures rather than relying on a promoter's estimate.
What goes wrong is that families plan the move for the petition date and then live in limbo, or, conversely, receive the visa and then delay the move for a year while the child finishes school, only to face abandonment questions. Fix the household's plan to the visa issuance: sell or rent the Canadian home, arrange the child's school and the parents' activities so that residence is real from the first admission. Then calendar the removal-of-conditions filing in the ninety days before the second anniversary of that admission, because missing that window ends the status.