Spring always makes me think of flowers and trees. How about starting flower/vegetable seeds in cleaned out baby food containers or paper cups (clear works better so they can see the roots)? That lends itself to all sorts of educational materials and games that are age-appropriate. Or you could have them make tissue paper or sun-catcher flowers.
Our FRC hold a Spring into Math night. This year it will be after Easter. They have a booth were you can make the Easter Bunny some food by mearsuring out oats and glitter. They also use pipe cleaners and cereal to make bird feeders. Each booth the kids get Bunny Money which they spend when they hop to the bunny shop to redeem their prizes. Ice cream is also served after you have completed all the booths. They usually have name tag necklaces made from with lamenated frogs or rabbits.
When I think of Spring, I think of baseball! Lots of things you can do with that. What exactly are you looking for? We play math baseball, but you could do trivia baseball with different levels for children and parents. Serve hotdogs and peanuts or Crackerjacks.
We are having a Spring (Eastery) Family fun Night on April 6th, and each grade level has a different activity for the children to participate in. I teach second grade, and need some ideas for something Springy.