If you're looking at a "roughly 2x to 5x" increase (40 to 200-odd), you have maybe 1 or 2 steps in there. Rough guess is "direct linear extrapolation is a factor of 2 of correct"" (given same time and same approximate macro- and micro-culture). If what you had now was sufficient, scale it directly by the numbers and add half again of the non-perishables and you will at worst look a little bit stingy and at best have non-perishables for next year.

Yep, used to do food planning for student functions and small-ish dinners-for-friends (seldom more than 20 guests, so "small"). Knowing your target audience is key in these things. Oh, also used to run the concession stand for a gaming convention. I have a rough feel for how many pallets of soft drinks you need for every hundred con-goers.