Camping Heaters for tents

cold weather camping what can i use for inside floor?
in 2 weeks kids 7 (18) going camping might be 30 degrees at night. taking very thin and big tent have tarp for over and under and two heaters for inside(will vent). what can i use to insulate the floor cheap i have another tarp that i can lay inside on floor will that create moisture? anyone use any other materials.
We use beach blankets. They’re nylon on 1 side so dirt and sand doesn’t cling to it, the other side is a thick cotton material. Great insulator and comfortable to sleep and walk on. It’s the right time of the year to buy them now!
