Have your students write an email/letter to a pen pal inviting them to go to a soccer game or to the movies!
Each prompt has some lesson-specific vocab for our textbook, but this could be adapted to whatever lesson you use -er verbs and aller! This is a good way to reinforce your students' knowledge of -er verbs as well as strengthen their knowledge with irregular verbs.
This could be graded with a checklist or a more detailed rubric. The one I used is attached at the end of the document. (Adapted from ACTFL Proficiency Rubrics for Novice Mid-Intermediate Low)