Invitations haven't gone out yet so can't be sure, but my gut tells me we will have lots of vegetarians.

For pre-arrival snacks:
2 large fruit trays from the grocery store
grilled pita, hummus (need to know how many lbs of hummus, please)
100 small spanikopitas

lunch will be a greek salad 2 wraps per person. Was planning on 100 vegetarian wraps (2 different types) and 100 gyros.

Do you think I need more variety than that? Other options for wraps are tuna, ham, and two kinds of chicken (pesto and picatta).

Dessert will be "strawberry shortcake" cake for 100 people. Do I need to have another option in case people don't want strawberry? And if so, for how many people and do we take that out of the size of the larger cake?

pita for dip- consider 1 ounce of pita chips per person), OR 1/2 6 inch pita, cut into 3 pieces. 1/4 cup hummus per person, and you might consider getting two flavors, there are so many available now.

Unless it is 1/2 vegetarian, I would do about 140 gyro and 60 vegetarian wraps. Get Tzatziki, 1/4 cup per person.

You might consider 4-5 dozen Greek cookies as a side dessert.