Water painting - Get cheap $1.00 paint brushes at the discount store and give each child a plastic bowl of water. Let them "paint" all over the house, driveway and sidewalk.

Water writing - Save up your old spray cleaning bottles and dish detergent bottles. Wash and rinse them well and fill with water. The kids can write with them or have water battles by squirting each other - you too probably so be prepared with the proper attitude.

Set up a water course

Break out the hoses, sprinklers, and baby wading pool. Let your kids design a water obstacle course or play traditional games in the water.

Water balloons

You can have loads of fun with one bag of cheap water balloons. Fill the balloons with water. This can be fun in itself. The kids always like to see who can make the biggest water balloon before it bursts or who can make a "baby" water balloon.

After you have your balloons filled, have a balloon battle, play toss, play water balloon baseball etc.

Hiking

Free and great exercise. Do I need to say more? Check with your state parks website and you'll find plenty of nearby walking trails and hiking trails to keep you busy. Pack a light lunch and drinks and you have an activity that will last the day.

Biking

If your kids would rather ride than walk, air up the tires and take off. You can ride through quite neighborhoods or most walking trails will let you ride bikes on them also.