Serve a Bring-your-own Banquet
Have your loyal subjects provide a potluck. Request dishes they deem "fit for a queen," something they would serve the Queen of England if she happened by at dinnertime. (It almost guarantees a lack of three-bean salad.) To ensure variety, ask guests to RSVP with their planned dish. Reserve the royal right to suggest a change if needed. Those who are challenged in the kitchen might help with cleanup.
If you're uneasy with amateurs, tap the pros-in-training at a culinary school's teaching restaurant. The staff is highly motivated -- everyone's grade depends on your satisfaction.
You may want to spring for a professionally made cake. Buy a plain cake and adorn it with store-bought decorations or fresh fruit.
Another low-cost (and trendy) option: cupcakes. They can be just as stunning to eat. Figure on one per person plus a few extras and eliminate worries about expensive leftovers.