mother's day lunch---mostly prepared the night before
You might take a look at Ina Garten's roasted salmon salad. It's a Nicoise composed salad with salmon in place of tuna. I've tweaked the recipe a bit, but have made it a number of times, and it always is well received. Everything can be prepared the day before, including the salmon. I will say that I've used my own dressing in place of the one in the recipe, so I can't vouch for that.
Do you prefer a veggie, meat, poultry, or fish dish?
You could make a quiche-I've always had rave reviews with Thomas Keller's very filling, deep dish quiche recipes. (A quick google search will give you lots of results for his recipes)
You could make a lasagna or Greek pastitsio or cannelloni Sat night and reheat before serving.
Since all of these are heavy dishes, a nice salad would be a perfect side. Maybe a fennel and orange salad.
You can also wrap asparagus in prosciutto the night before...