Last year the executive team came in and made pancakes for our staff.  Because we're in Louisiana we played some cajun music and wore our most outrageous aprons.  We had a flipchart with show appreciation to your team with post it notes.  By lunch there was a ton of appreciation shown that everyone could read.

Hi. Christina's thoughts are great and fun. Here are just a few other quick ideas given the timeframe you have.  Company paid for gift drawings/raffle type activity; highlight groups or teams  that had clearly exceptional results as a form of recognition...make it fun/quirky;  if you're doing some kind of presentation, have a page that highlights and celebrates people w/ long service...could also do on your internal website; etc. .  Lots of ideas on-line.