Some easy "pranks":
A drop of food colouring in the PMC's white wine glass before everyone sits down always brings a smile (albeit not from the PMC).
Talc in the napkins.
Talc in balloons which can be chucked down a leg of the table until it gets too close to a candle..... Cue one particularly boring H&S guy to state that we couldn't drink our "contaminated wine"...yeah whatever....
A remote controlled helium ship can particularly annoy the PMC and/or Harry Staish during speeches. Feel free to add a "dropping" device!
Just make sure that no honourary members set off "crow scarers". Carnage....
Enjoy