After 2 seasons of camping with our now 3 and 7 year old, we felt we were ready to endure some lower temperatures in the early season. To hedge, our bets we decided against tent-camping and tried one of the cabins at Harper's Ferry Adventure Center. It turned out to be plenty comfortable and a fun experience for all. The cabins are insulated and have a single electrical outlet which accomodated a space heater we brought. The night got down to 45 but we were actually warm enough to require shutting the heater. We slept on a set of 2 bunk beds in the small cabin, despite the early arguing between the kids about who would get the 5th space up in the loft made out of the porch overhang.
7 yo Shea dominated the rope course, and they were so impressed with her being one of the youngest making it to the "3rd level" they gave here a free t-shirt! They have a gigantic "pillow-bounce" that is a trampoline to the extreme. In the summer there is rafting and other water sports. Harper'Ferry is 5 minutes drive and is a great historic/natural experience. The national park there also has additional camping.
We will definitely be back in the summer with our tents!