Is there a way to halt or redirect the creative process when the timing is poor?

Here is the situation - got a big family Halloween party on Saturday.  Looks like it will be cold and rainy so all guests will be in our house - which  is not huge. 

Still have cooking to do, party set-up, last minute cleaning.....

My daughter is making a pinata for the party.  Today my ADHD husband was driving down the road - saw some  fluffy milkweed and thought - hey, that will make a great covering for the pinata.  In comes all the wet wild weeds, out comes an old screen door, laid out in the bathroom, where my spouse spreads out all the fluffy stuff to air dry, then he covered it with newspaper, then he taped down the newspaper, all amidst my trying to do party prep.  Arrrgggghhhh.  It still will need to be glued to the pinata.  Messy enough without the flying fluffy weeds.  

Positive ADHD - very creative.  I see the glee in his eyes.  the creative juices flowing.

Negative - Poor timing for the messy art project.  In the middle of my trying to get ready for a party.   And it is plugging up the use of the only downstairs bathroom. . . . . . . and taking lots of time in which I could enjoy his help in the party prep.

Hyper focus on what he is doing.  Oblivious to me and my frustration . . . . . . Puh - lease. . . . . . . . this is the type of thing I deal with a whole lot.  

Any previous attempts I tried in curbing this sort of thing evolved into a big disagreement.