Take a few chairs and drape a blanket over them to make a tent.
Lay a blanket on the floor to camp on.
Read books, eat a snack, sing campfire songs, and snuggle in your tent.
For Older Children:
I suggest making indoor s'mores with your kiddos. You can make them in the microwave OR toast the marshmallows over a candle (put them on a skewer first!). And of course provide supervision!