You can write saying how fun your vacation was in Hawaii and explain what you seee, the waves, turtles, what island you went on. Lets say you went zip lining or went for a helicopter ride on your vacation! you can also say what has been going on at home and what chores you have to do if they are boring or not. Ask about your pen pals culture and explain yours as well! Always try to use better words ( dont use Pero use Aunque) You can also have a paragraph about how your school year is going and that you are making friends or not making friends. Say you just moved schools, you can write about that! El carta no va a ser real!
Mi vida en 10 años probablemente será genial. Pienso esto porque puedo conseguir un buen trabajo como médico u otra profesión. Como médico u otra profesión muy importante, puede ganar mucho dinero y hacerse rico. (I started it off for you)