Structure the closing so funds are committed before the interview but ownership and possession transfer on or after visa issuance. Closing outright months before the interview leaves the inn running without an authorised operator; closing only after approval risks a finding that nothing is yet at risk.
Commit first, take possession second
The interview must find the investment already at risk, yet the couple cannot lawfully run the inn until the visa issues, and a seller who has been paid will not want to keep operating it. Hypothetical example: the Lake Country couple sign a purchase agreement with a deposit and full price in escrow, a closing date set for thirty days after visa issuance, and a clause allowing the seller and nephew to continue operating in the interim; this satisfies commitment at the interview while keeping the inn lawfully staffed. If the seller insists on closing now, the couple should retain a manager who can operate the inn until they arrive and avoid directing it from US soil on visitor entries.
The Canadian property sale should complete first so that the funds are traceable, and the operating agreement with the nephew should be signed before the interview so the officer can read the control terms. Build the calendar from those three dates: sale, escrow deposit, interview.