Manual activities that they can get involved in: make play dough, beads on a string, decorating paper planes, dress up, lego, build a track for toy cars. If you can fill a bath and let them play in it. Mine could splash happily for half an hour. With some effort you can play pass the parcel, or assign to each of them a sound to make and you are the conductor like in a band. Darken a room and give out flashlights. Build a fort/castle.

Good luck!

Pillow fort, baths, messy art? (Ok maybe messy art and THEN baths)

We have three: ages 1, 3, and 6. Our go-to move is to get them outside. In the driveway or yard, going for a hike, to a playground, etc. Anything outside keeps them sane. The longer they are inside the more insane everyone becomes.