For the Greek salad, suggest you use the village salad under the salads that hold section in Big pots, made ahead, with the romaine added day of. You do not need a second lettuce salad. Instead, consider doing the antipasto vegetables, 3 gallons, also a make ahead.

A self serve buffet for 100 people requires about 3-4 people in the kitchen, day of, plus servers, and they can't be part of he wedding, as they will be setting up during the service.
It is CRITICAL that you consider having appetizers, and serve them before the meal! The guests will be standing around for nearly an hour after the service while you do photos, etc. and your staff is trying to get the buffet set up. Here is a quote from my upcoming article:

A self-catered buffet is a real challenge to the organizers, and things don't always come together as smoothly as hoped. By planning and setting up an appetizer area or "nibble table" which is ready when the guests begin to arrive, the cooks and servers have time to complete the arrangement of the dinner buffet. This is especially critical if there are children among the guests, or there is a wait before dinner, as at a wedding reception.

This does not have to be complicated. Three items, plus a punch, or two if one punch is alcoholic, are sufficient. Typically, include a fruit tray, a cheese tray and an attractive dip or spread; or you can go with a dinner theme such as TexMex with chips, salsas, Texas caviar and guacamole; maybe shrimps if budget permits.

One appetizer service area is needed for each 100 guests.

You can see amounts on the fruit tray page and the veggie tray page. For dips/spreads, 1 pound bread or chips per 10, 1/3 cup per person if there is only 1, or 1/4 cup each for 2. I would not put the appetizers on the tables but in a separate foyer/bar/waiting area, I would keep the guests out of the serving area until the buffet is ready to serve.

For 100 people if the pizzas are deliivered, I would plan on 3 in the kitchen and 6 experienced servers to set up, serve and clean up. With 100 guests, you need 2 serving lines or a double sided line to serve everyone in under an hour.
This should include some very experienced people. Culinary schools, local diners that close at 2 pm or active church or school kitchens are some sources for staff.