No need to react.
If I am alone, there is no body to stare!
i would yell out, it wasn't me !
"Is everybody here? Great! I'd like to thank all of you for coming to the meeting. Unfortunately, the keynote speaker couldn't come today, so while I pass the hat, I'll be entertaining you with a little number.....Please give with your hearts folks- it's for a good cause....."
If folks are gonna stare, you might as well enjoy it. :)
smile and continue on like Im the queen of the ball ;)
Stay calm and ignore them all.