The easiest fish dish I've served for a crowd is simply baked fresh halibut or cod
The hardest part will be separating the pieces so the thickness match. I start baking the coated thickest pieces first for a few minutes and then slide in the coated thinner pieces. That way they all finish at the same time (for 1" thicknesses, it can run from 10 minutes to 20 minutes).
Butter pan heavily. Rinse & blot dry the fish pieces and lay together, bumping them up against each other (but not overlapping) to keep moist. Season lightly and coat top and sides with a 1:1 blend of honey-mustard and mayo. Coat well with either dry bread crumbs or with 1:1 crushed potato chips:toasted fresh bread crumbs. Drizzle with a good amount of melted butter.
NOTE: For some reason, this works best with dry crumbs and drizzled butter--rather than mixing the butter into the crumbs and patting that on. Don't ask me why...I have no clue plus it's not logical.
Bake 400 degrees for 10-20 minutes...until top is golden and the butter and bread crumbs are bubbling around the edges.
Really nice to serve with Evelyn's briani (crusty, cheesey potatoes)