When my kids were little, and I wanted non-TV quiet time (to cook, or pay bills, or whatever), play dough was a lifesaver! It still works for my seven-year-old. And she LOVES beads (regular beads for stringing, and Fuse Beads).
If they're first graders or younger, a big plastic tub of rice is a great activity. You can bury different things in it for them to discover, they can use scoops and bowls in it, little trucks are great in there...
Together, going for a walk is nice.
