When I book a wedding I get an expected guest count from the client and base the quote on what they expect. I then use the guaranteed guest count as a "minimum" they have to meet in order to honor the pricing. I would rather use the expected to give the quote on the higher side of what the final bill would be rather than the lower or guaranteed number.

Currently I am using the event I create to enter expected and guaranteed. From there my contract pulls the guaranteed number from the event and automatically enters it.