Welcome to the forum! You might want to wait until AFTER the party to shock. That is when there is more likely to be YUCK in the pool.

In a pool your size, a gallon of bleach will raise your chlorine by 3ppm. (Remember, usually bleach is not sold in gallon jugs anymore. Typically the jugs are only 3 quarts instead of 4 which is a gallon.) Shock level for your cya level would be around 15.

Have a great party!