You can never be overdressed on the QE2 take your ball gowns,and finery i am sure that you will have a absolute ball.
You won;t be out of place, but just as an aside, I found the quality of evening wear to be disappointing on a recent QE2 cruise (Fire & Ice). Sadly, the worst culprits seemed to be women in their 50s many of whom thought that through a shawl over a standard blouse somehow made it "black tie".
Also, Cunard goes on about dress code being strictly enforced. I saw a number of people on a number of nights wearing casual dress and not being challenged.
For me, the dressing up in the evenings is a big part of a cruise (makes it feel special and different to a hotel holiday), so I was disappointed.
But hey, dress up in your finest... as the previous answer says - you will have a fab time.
Look at the website www.aroundtheworldin80dresses.co.uk. She was on this year's world cruise on the QE2 and the site is very informative.
As a gentleman I love to see the ladies all dressed up they add sparkle to the formal evenings.