Help W/ 1940`s Theme Party Ideas Please!!!

Hi!
I am looking to plan a 1940`s themed birthday party and am wondering if you have any suggestions as to what we could use for decorations or props, as well as what to do for activities and what to use for a cake. There is only a small crowd coming--10-15 people, all older, and it is going to be a dinner party. If you could be of any help it would be very greatly appreciated because we haven`t been able to find much to help us on the internet. Also, there is a Irving Berlin emphasis in the party theme, as well, if that helps at all.
Thank you very much!
Susan