Do not assume an oral assurance grants immigration permission. Clarify actual employment and the required process before relying on a start date.
Keep the next step concrete
The business conversation and government authorization are different events. Describe changes honestly rather than treating the initial contact as approval.
Use that deadline to obtain the acquirer's written confirmation of your employer and duties, so any necessary new letter or petition is ready in time rather than assembled during a delay at a port of entry. List every dependent's step beside the party that controls it: the consular post controls appointment availability, a registry controls how quickly a certificate is issued, an inspecting officer controls admission on the day, and the employer controls the start date. Because admission is decided on arrival and the period granted is tied to the employment described, applying against a schedule that has not settled produces either a refusal or an authorization that no longer matches the work. The immigration step is usually the shorter one; an admission in TN status can be sought once the letter and credentials are ready, and admission is granted for a period set by the officer, with extensions possible while the employment continues.