Keeping in mind your plan to continue with the other personal pronouns and and their respective forms of the verb “ser” another day; you can now move on to the verb ‘estar’.
Try for example”Yo estoy en la clase” ( I am in the classroom), and pick out a student and ask “¿Roberto, dónde estás? to which he would reply “Yo estoy en la clase” or teach him “Yo también estoy en la clase”. Continue with other students in the class.
Now make an unhappy face and try “Estoy triste” to indicate that estar is not only used with place, but also description.” Then make a happy face and try “Estoy contento(a)", and have the students follow the pattern. Now, ask “¿Estoy triste o no”? “Estoy contento(a) o no”? to have them practice negatives and asking questions.