Why not make Magic Mud and Slime on the same day. Both use pretty basic around-the-home ingredients with pretty different results! It's amazing what white glue does when combined with borax. Dare to compare!
I found this helpful pdf online, by chemistry teacher Dr. Jim Hebden, which takes you through the process of making slime and carefully cautions you about the dangers of ingesting borax (therefore this project needs high supervision, especially for your little mouthy folks).
Here's the gist:
1. In one container dissolve 1/4 teaspoon of borax in 1 Tablespoon water
2. In a separate container, mix 1 Tablespoon water with 1 Tablespoon white glue
3. Pour the borax solution into the diluted white glue while stirring slowly (about 20 seconds)