The correct conjugations of the verbs between parentheses are:
1. Tú lavas el auto antes de ir a la fiesta.
2. Nosotros nos bañamos antes de ir a la fiesta.
3. Para llegar a tiempo, Raúl y Marta acuestan a los niños antes de salir.
4. Cecilia se maquilla antes de salir.
5. Mis amigos siempre se visten con ropa muy elegante.
6. Julia y Ana se ponen los vestidos nuevos.
7. Usted va a llegar antes que los demás invitados, ¿No?
8. En general, me afeito yo mismo, pero hoy es un día especial y el barbero me afeitará. ¡Será una fiesta inolvidable!
Explanation:
Almost all the conjugations of the verbs was written in Present Tense, but the last was written in Simple Future, the reason is because in the last sentence of the eighth paragraph, uses the verb "será" and it refers to the future, then, the second part of that paragraph must be in future.
In some sentences must be used a form of object pronouns as "se", "me" and "nos", these are used where the verb implies actions that are executed on the person who performs them, for example, dress, shave or bathe, if these actions are not received by the person that performs them, it's not used the object pronoun.