Little kids love play dough, especially the kind you make yourself that smells so good if you add a drop of peppermint. The reicpe is just salt, flour, cream of tartar, peppermint, and food coloring - do an Internet search for it. Making it with them is lots of fun.
Make hand puppets from old socks and decorate a cardboard box to make a stage and do puppet shows.
All kinds of singing and dancing games, and musical instruments. You can make your own musical instruments with them - rhythm sticks (wooden trowels, whatever works), shakers (empty containers with something inside and securely taped closed), drums (using ice cream containers), etc. YOu can also buy simple ones quite cheaply at dollar stores.
Read them lots of books and stories that have lots of rhyming words or language that repeats and they quickly learn to "chime in" with some of the words. Check out the children's corner at your public library. They often have a little kids story hour run by volunteers.
Learn nursery rhymes and counting rhymes with them.
Do little cooking projects with them - cookies, special snack foods. Crackers with peanut butter and raisins, apple slices, grated carrot, etc. to make faces. Bananas dipped in melted chocolate. Homemade Mini pizzas they decorate themselves with their favorite toppings.
Building blocks and magnetic letters and shapes give lots of ideas.
Any arts and crafts activities, but they especially like finger painting. You can also get recipes on line to make your own finger paint.
Do printmaking projects with them. Cut potatoes in half and use them to do printing projects (cut a design in the cut side of the potato, paint the cut side or dip it in paint or on an inkpad, and press it over and over again onto a large sheet of paper to make a pattern). You can use lots of objects to do this sort of printing/stamping project and it is much more fun for them than the stamps you buy.
If I think of more I'll edit this. Hope it helps.