A good question.
A local answer.

Snow at a forecast elevation does not guarantee safe access or a usable snow-play area.

Check the forecast close to departure and pack layers for morning and evening changes.

Treat peak colour as weather-dependent and check recent local garden or tourism updates near departure.

A winter stay can work well for galleries, cafés and short city walks if you pack for cold mornings and evenings.

Photograph from a lawful public viewpoint or road stop with safe parking. Fields are working private farms; avoid gates, crops and roadside shoulders without space.

A few nights can cover the main city sights; a longer stay makes sense if you add regional walks or day trips. Do not fill every cold day with driving.

Check the garden's current season dates, location and any event shuttle first. A suburban bus route is unlikely to take you right to a rural entrance.

Choose a car park based on its all-day rate and access to both the shuttle and city shops. Check closing time and event road changes.

Compare Canberra and Melbourne by the actual resort you plan to use, the road transfer, car hire and accommodation. An airport's distance alone does not tell the whole story.

Peak colour changes with the season and the exact neighbourhood. Late March can be early in some years, so keep expectations flexible and check current local photos nearer your visit.

Pack layers for cool mornings and changeable afternoons, then check the forecast just before travel. September averages are less useful than conditions on your actual days.

Plan another scenic stop in case the fields have finished flowering. A drive based only on an old photo can disappoint.