Teach your kids a new sport, or practice their favorite with them.
Fly a kite. If you're feeling extra ambitious, you can build a DIY kite first, then try to fly it — but a store-bought one works fine, too.
Host a sidewalk chalk art show.
Lie on your backs and check out the clouds.
Go on a walk around the neighborhood. If your kids are lukewarm on this idea, suggest going on a color walk (where you try to spot items that represent each color of the rainbow) or an alphabet walk (where you pick out items that represent each letter of the alphabet).
Blow some bubbles.
Host a super-sudsy car wash. Bonus: its a chance to get some of that sticky spring pollen buildup off your car.
Dine al fresco.This works for any meal of the day — or all of them.
Try "water toy painting." Change your kids into their play clothes, fill water squirters with watered-down liquid watercolor or other washable paints, bring them and a large poster board or old sheet outside, and let them spray the colors at the canvas, creating a Jackson Pollock-like masterpiece.
Go stargazing.
Pitch a tent in the backyard, and sleep under the stars.Or just use the tent as a temporary playhouse, and head back inside for bedtime — it's a fun activity either way.
Play frisbee.
Pick weeds. There are always plenty in the spring. This can be surprisingly fun, and gives your garden or lawn an uplift, too.