With a wedding dinner, I always recommend an appetizer plan, and here is why:
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.

One appetizer service area serves about 100 guests.

Your salmon could be the backbone of this service, add fruit trays and cheese/cracker trays and you would be in good shape.

This leaves brisket, shrimp pasta and salad. I plan to include a dish that can be used as an entree serving for any vegetarians, side dish for others. Also, unless you want everyone taking both brisket and shrimp, you need to add in a hot or cold starch dish for the brisket eaters. How about scalloped potatoes? That could meet both needs. I also recommend one cooked veg. This could be, for example, roasted veg served at room temp if cooking space is a challenge, or a veg casserole instead of the scalloped potatoes.