The use of a water dropper is a very good way for the kids to develop some really good fine motor skills. The concept of squeezing the dropper to release the air then placing it in water and releasing to suck up water is a concept that will fascinate the kids. NOTE: make sure you have your patience ready because this a concept that might take a bit for the kids to figure out. :)
Project for the dropper:
Color coffee filters with markers then have the kids squeeze water out of the dropper onto the coffee filter. The colors will run and blend together. After it is dry you can bunch it up in the center and use a cloths pin to hold it together and it will become a beautiful butterfly.