I think the first thing we need from you (the OP) is either a breakdown or at least a total of your actual incurred
costs here, before yours and your helpers labor time is even considered, (and your company's profit on top of that)
just as in catering you would first list out your food costs and other fixed and variable expenses, both direct and
pro-rated. In this case, as mentioned above, insurance for the valet provision would need to be written in, just as
liability ins would be if you were prepping/ providing food. Once you have those figures, you can add in what y'all
want for your 6 hours work, plus your planning time, etc.
Also as mentioned above, we're unclear as to who IS providing the food-- their family and friends, or some other
caterer, so to me it begs the crucial question as to who is to be held responsible for the quality/safety of that food
from the time you take control of it to the time it finds the guest?
As server/valet/bar you logically shouldn't be, but that doesn't mean you won't--my concern is that if you're a
licensed caterer, serving food that someone else (especially if unlicensed) made ,and there's a problem, I'd hate to
see you being the one holding the bag. If this is a possible issue, you might want something signed by the client,
legally absolving you of that liability. If it can even be done,depending on the actual facts here.