In Michigan, we are just now starting to have really nice (and warm) days where the sun actually decides to shine. Take advantage of those days. Get outside and play in the sand, play soccer, play tag or get the water table out and let them play with rocks in the water.
We love kicking the soccer ball around and doing kickups and it's been a joy teaching the kids to kick and make goals, they're so proud.
No matter what you do outside, just get out there and enjoy the fresh air and sunshine.