Here are my most favorite experiments I've found for a three to four-year-old. MAKE ICE GROW
Leaf Identification Cards put in sensory table or on discovery table along with realleaves! They could use them in sorting and classifications of the leaves.
Science for Kids 30 FUN Science experiments perfect for toddlers- We have done a few of these, and my kids were in awe! Really want great tips concerning arts and crafts?