The best place to start is
http://boards.cruisecritic.com/ - from there you click on the link for Cunard and you will find a whole heap of useful info about the ship. You can join [it is free] then you can post questions. Another really useful link is a bit further down that main page under Roll Calls - again click the Cunard link and you can 'chat' with people on your cruise - great way to find if there are any other children on board.
You cannot see the Roll Call unless you are a member though.
This is the most useful site for cruises that I have ever found - and it is quite addictive!
As for what to wear - I think you will find that this question has been asked there a few times!
Happy cruisin'