I took some behind-the-scenes photos during the day.
Walking among some 300 balloons. They started moving, wandering, by themselves at some point. Freaky (and also totally explainable).
It was a rather long but hilariously silly day.
You can see the result here - this will most likely open up more for those born in the 70's and 80's that attended school discos in their pre-teens. And have video footage on VHS of that...
(The disco-sign on the door was suitably there when we arrived already, as a remnance from the last party of the year.)