are you near a railway line. At that age, I got a lot of mileage out of taking them on a short train trip to another suburb, picking up a coffee/snack or having a picnic at a park & then going home.
Is it warm enough for water play, mine loved being in the "shell" with about 15cm of water, or even a few buckets & cups & sponges?
Could you do "play cooking" making glup with cornflour & water, or just a bowl of dried stuff like rice, pasta etc that they measure & pour into a bowl & pretend to cook... my DS1 had hours of fun with that at 2yo when DS2 was a newborn... he even played in the "snow" outside with a whole lot of flour.