I am not sure if these sentences for "is to do" are right?
-A leader of the organization is to annouce about new activities. -I am to do homework due to tomorrow. -My family will be to pack some stuff in the box next week. OR My family is to pack some stuff in the box next week.
The grammar of your sentences (regarding 'to be to + infinitive) is correct. However, it is a rather formal future form, so it sounds a little odd in your 2nd and 3rd sentences.