Here are some ideas I saw...  some worked well, others didn't:

Violet - Her "mother" pulled a rag out of her purse and acted like she was trying to wipe the purple off her face when in fact, she was applying the purple. 

Also, most of the characters that needed to change or disappear simply went behind a curtain and in some cases was exchanged for a double.

The boat scene was done by using a cut out of just the front end of the boat.  All the characters were behind this "boat" while a video played on a large screen behind them.  It gave the effect that the actors were traveling quickly down a tunnel.  The same effect was used with Grandpa Jo and Charlie as they were "floating up" in the bubble scene.  In reality, the video was moving downing creating the effect. 

As our performance date moves closers, I'll post our special effects once I come up with them!