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!