Walks in the park showing them birds and flowers and all the things in the park Go to the swings and sing songs and counting games when you go up and down stairs or steps. Nursery rhymes are good.
Building blocks and stacking games.
Books. They might get a favourite which you have to read over and over again. But that's good.
Talking about anything and everything. Smelly things, like fruits and such like.
Touchy feely stuff. Things that roll and things that don't by way of contrast. Children love balls. Balloons, bubbles.
Musical instruments, tambourines, bells, drums.
In other words variety, lots of.
A goody bag with different kinds of things in it. Furry things, puppets, crinkly paper.
Things they can push.
LOL. My house and garden can look like a nursery. They never stick at anything long at that age.
If it's really hot, water games. A baby bath will do with things that float and sink and things to pour.