i have a 10 and a 4 year old, but i enjoy a lot with them. we still make those paper boats and float them around in puddles near our building. also, we go to nearby water bodies and sit there, sometimes getting drenched in the rain and enjoying the breeze. it is also fun to play with the kids in the garden when its not raining too hard, and let them play barefoot in the lush grass. me and the kids also love looking out at the rain while sitting by the window, and my younger one sings out her favourite poems or does her activity books.
i have a 3 year old and we love spending time together doing fun things in monsoon! as debolina also mentioned, my daughter makes paper boats and we play with them in the puddles outside. it is also a great time for her to have her hot chocolate, and she loves making it herself while i watch her. she also loves to wear her raincoat and take a walk in the rain with me.