It is critical NOT to multiply baking recipes above 4 times, and yes, you do need to adjust the baking powder. Use a tested food service recipe for 48-50 servings and do 3 batches.
Here is the Navy recipe for 2 18x26 pans (108 pieces) to use as a base.
FLOUR,WHEAT,GENERAL PURPOSE 3-7/8 lbs 3 qts 2 cup
CORN MEAL 3-2/3 lbs 3 qts
MILK,NONFAT,DRY 6 oz 2-1/2 cup
SUGAR,GRANULATED 7 oz 1 cup
BAKING POWDER 5-7/8 oz 3/4 cup
SALT 1-1/2 oz 2-1/3 tbsp
EGGS,WHOLE,FROZEN 1-1/2 lbs 2-7/8 cup (can use fresh eggs, same weight)
WATER 7-7/8 lbs 3 qts 3 cup
OIL,SALAD 1-1/2 lbs 3 cup
COOKING SPRAY,NONSTICK 2 oz 1/4 cup 1/3 tbsp
Blend flour, cornmeal, milk, sugar, baking powder, and salt in mixer bowl.
Combine eggs and water; add to ingredients in mixer bowl. Blend at low speed about 1 minute. Scrape down bowl.
Add oil; mix at medium speed until blended.
Lightly spray each pan with non-stick cooking spray. Pour 1 gallon of batter into each pan.
Using a convection oven, bake at 375 F. for 20 minutes or until done on low fan, open vent.
Cool; cut into 6 by 9.
In step 1, omit sugar if southern-style cornbread is desired.