My go-to trick for keeping my kids entertained is setting up scavenger hunts around the house. You can tailor the difficulty to the age of your kids, and hide things accordingly! It keeps them occupied for hours, especially if you make it an ongoing thing with clues leading to more clues.
Also, if you have access to a backyard or a park, a nature scavenger hunt is fun and educational - collect leaves, identify birds or insects, that kind of stuff.
For at-home arts and crafts, I keep a rotation of simple supplies on hand: paint, paper, glue, scissors, and plenty of sticky tape! It keeps down on the mess factor and the kids can make all sorts of creative things.
If you're up for a little bit of prep work, freeze some small toys or marbles in a block of jello, then set the kids loose with a hammer to excavate them. They seem to really enjoy the novelty of smashing stuff and extracting the prizes! Safety first though, obviously!
Good luck and happy parenting!