Use the plan for 100 page for the salads. 3 times the amount for 100 for EACH of the salads, since they are 3 different types.

For the potatoes, see the recipe at the bottom of the festive family brunch page.

You need to plan for at least 85% of the invited guests and you need an appetizer table.

Serving a large number of people as quickly as possible takes planning. Since each person can easily take a minute in the line, for the fastest service, it is a good plan to have one service line for each 50-75 diners. This article outlines laying out the service lines for your buffet.
Before the Buffet; Why You May Need an Appetizer Table
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 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; Italian with bruschetta or antipasto; maybe shrimps or other cold seafood, if budget permits.