Invis,
If you are serious about floating a small item in an old folks home wearing a gas mask I think you should consider the strength of your fear factor.
You obviously want to scare the sh*t out of them, so I would suggest first effect should be 'Floating the Atom Bomb' and not a little blob.
Follow that with a multitude of flash paper and a devastation of half of the dining room.
Finish off with a reveal, 'I poisoned your water you had with your supper' might be a good one.
If any remain alive, try Electric Touch, it will knack their pacemakers !!
Being as how you are wearing a gas mask, hand out cards as you leave saying, 'My name is Tony Blair'
You are on to a winner and will likely obtain financial backing from the government who want any profitable method to get rid of the old folk who are an increased burdon on current dwindling funds

Tenko.
Yorkshire, UK
Male, 55yrs old, Retired.
"I don't believe it" Luke Skywalker
"That is why you fail" Yoda