Question about wedding balloons falling from the ceiling?

Can you answer Reese g’s question about Balloons?:

My fiancee and I are getting married and we’re going to be doing it outside in a large gazebo type thing. We want to have the whole falling balloons thing right after we say “I Do” our guestlist is small and we’re doing everything ourselves. We were wondering how would we make the balloons fall from the ceiling of the gazebo? Please keep it low tech.
Btw I didn’t ask for opinons, so please either answer the actual question or don’t answer at all. Thank you.
The gazebo will be at a lake, its a public outdoor gazebo, doesn’t belong to anyone.

Have you claimed your Genesis site?