Making simple crafts with young children helps a lot in increasing their attention span and developing fine motor skills. Kids love messing with colors/painting with their fingers. Making cutouts of different animals and finger painting all over it is an enjoyable activity for the children. They might also learn a thing or two in the process.
Here are a few pictures of the crafts that I made with my pre-schooler (some ideated, some inspirations picked from the web)
Clothes Pin Alligator
Frog with Sticky tongue
Leaf cut out of paper plate, Cocoon made from cotton & Caterpillar made from Green peas