Party or Assignments

I was invited to someone's birthday party. I replied immediately that I would attend it, but next week has a lot of assignments coming. 1 short presentation of my learning portfolio, 1 long group presentation, and I have to prepare for a prop box. I didn't want to cancell on it, but I think I have to... Next month, last month of this semester, luckily, things will get slower, so I will try to have a rearrangement for it.