I was just looking for things like this too, especially things we can do inside AND outside on the days when weather doesn't cooperate. Here are some of the ideas that I found online.
Bean bag toss - you can make your own bean bags with kid socks that you fill with beans and tie off at the end and you can use a laundry basket to toss them in. You can also draw a tic-tac-toe board on the ground and use two different colors of bean bags to play tic-tac-toe with him using the bean bags to toss in the different squares.
Use duck tape taped to the sidewalk , patio or driveway to make a "balance beam" so that he can practice balance by walking it, skipping it, hopping it, and so forth.
Cut off the bottoms of liquid laundry jugs to make scoops with a handle and throw and catch a ball back and forth using only the scoops. Tennis balls are perfect for this.
Use sidewalk chalk and make a four-square or two-square court and play using a beach ball.
String up a line between two trees or two chairs and play a toddler version of volleyball. You can use a beach ball or balloons.
Go on a walk with the intent of collect things like rocks and leaves. Take a camera and go on an animal safari in your own neighborhood, taking pictures of the neighborhood animals and local "wildlife."
Let him "paint" the house with a bucket of water and a paintbrush.
Help him pick out and plant a couple of flowering plants that are his to take care of and let him pull weeds, water the beds, deadhead the flowers and so on.
I agree with one nice poster about sand, in that it can be a total nightmare. It gets everywhere and you can't seem to completely make it go away. But in that sand table you can put pasta, gravel, beans as many different things as you can imagine along with scoops, bucket shovels and such. You can even put treasures or fossils that you draw on bigger rocks and let him be a treasure hunter or paleontologist (sp?).
The large motor play and the outside play is so important for development and I think it's great that you are trying to meet those needs for him. The key is to change it up so that he gets to do something a little different from time to time and then you can save the park for days off and he won't feel like he's missing a thing.
Good luck and congrats on that baby!!
L.