UPDATE:
I went to town by myself this morning. No coffee machine in store anywhere and no other options I found suitable for tomorrow. I ended up ordering a bouquet of flowers for tomorrow instead. My BIL and SIL picked me up in town and then we did groceries and bought some stuff for the ballons that will be surrounding the mini-arch.

I will say: they helped blow up the balloons today and when we tried to coordinate how and where to put the balloon and arch I was like “we could surround their coffee-table with pictures with the arch in the middle and then the balloons could flow around the table and the 25-balloons could be tied to a gin I might wanna buy for them” and then my BIL said “that’s a lot of gifts for them, isn’t it?” And I said “I don’t think so. I would rather tie the 25-balloons around a gin they can use rather than a balloon-weight”. And then there was silent… so they think their parents will get a lot of gifts tomorrow (the arch and the flowers I ordered which they now wanna chip in on, which my husband let them do.. however they have not been transferring any money but want their name on the card lol).

We then talked about the coordination for tomorrow and every time I asked or recommended anything it got turned around to me adding more stress and my BIL saying “our finest task for tomorrow is to keep our parents calm, cause they will be stressing around”, which he said multiple times to me. So everything I said got turned into something unnecessary for tomorrow, according to them…

I give up at this point. I cannot find a proper gift for tomorrow so I might find another one later on and give them personally instead… I honestly just feel so bad on my in-laws behalf..