For this week's playdate we made Gak (a gooey playdough like substance). There were just 3 kids here for this experiment and they were ages 2-4.5. I would say that this project was fun for all the ages, but the end product was most fun for H (the oldest). It was a simple enough project found here:
Ours didn't come out that stretchy, but I think I just added too much borax too quickly. H is still playing with his a few hours later. The good news is, it also doesn't seem prone to stick in things like carpet or pets fur, make sure the little ones keep it out of their mouths though. I would even try this again to see if I could make it come out more stretchy.
H with his Gak!