Help! Workplace Bridal Shower

A few of my co-workers (bless their hearts) have decided to get together and throw a sort-of workplace bridal shower/luncheon for me. The problem is, I did not invite most of the people who will be attending this shower. Shall I ask my co-workers to cancel the shower? I simply cannot invite everyone my wedding, but I see these people everyday, so I dont want to offend anyone. Any advice would be appreciated!