The theme they want to use is "Life begins at 50". Also it has to be a sheet cake because it's an office and that is what is easiest for them to cut.
"Life begins" makes me think of a baby. Also a friend suggested the game of LIFE.
How about a modelled pc and screen...the writing on the screen says
" Life begins at 30 (cross a line through it ) 40..(line through it ) 50.