Take 2 large sheets or sheets of plastic and pin/sew/tape together 3 sides. Put a fan at the one open side and pin the blankets around it. Leave enough room to get in and out. Close the final opening with cloths pins (easily removed for quickly running in and out).
Cool Idea: Trampoline Tent: My brother and sister and I did a fair amount of backyard camping when we were kids, but if we'd had one of these trampoline tents, it would've been impossible for our parents to get us in the house.