Hi there, thanks for your query.
I'd recommend contacting a Tour Planner as they may be able to offer you a package to suit. A link to the Queenstown winter Tour Planners can be found here.
For information about Milford Sound Accommodation, please click here.
Cromwell may be a cheaper place to stay, but you'd need to allow an hour for travel time. Cromwell accommodation options can be found here.
Regarding visiting Dunedin, you'd want to allow 3.5 hours driving time from Queenstown, or 6 hours to visit Christchurch.
Regarding wine regions, they are dotted along the path between Queenstown and Cromwell and information about those can be found here here and here.