Lo que hice hoy

Esta mañana hice café y llevé a mi hijo a la escuela. Fui al banco para abrir una cuenta para mi negocio. Hice un poco de trabajo en Starbucks. Limpié mi casa. Jugué con mi gata. Cociné la pasta para el almuerzo. Cogí a mi hijo de la escuela. Ahora me voy a caminar hasta el parque.

This way it sounds better, because you were changing your tenses for no apparent reason. "He hecho", since you're talking about something that happened today, is okay, but it sounds really awkward when the rest of the sentences are all in another tense, and you're also talking about things that happened today. "Cocinaba" is like "I was cooking" in English; it is what we call co-preterite, which means it coexists with a preterite: it specifies something that was happening when something else (probably more relevant) took place. For instance, you could say "mientras cocinaba, llamaron a la puerta" (while I was cooking, they knocked on the door). Apart from that, I think it's some pretty decent writing.