The only "camping" with my three year old was just in the backyard. I guess its my way of easing him into actually going somewhere camping, and to test the waters / "shake down run". He's been sleeping in the tent in the back yard several times for the last year or so, so since he was two. The first couple times we did this it was below freezing, and he used one of my old sleeping bags, and slept on a twin blow up mattress. These nights made for very poor sleep for me because I kept waking up to make sure he did not fall off the blow up mattress, and of course just about each time I found him sleeping on the cold ground (inside the sleeping bag).
The weather warmed up, so I got him a cheap/simple Academy warm weather sleeping bag. During these warmer experiences he slept on one of our older ¾ length thermarest self inflating sleeping pads. I discovered these lengths are perfect for the little fellas, and i'm very glad I didn't toss them during a previous spring cleaning. He did pretty good during these nights. but still rolled off the sleeping pad. When this kid sleeps, he ends up all over his bed throughout the night.
For Christmas, Santa is bring him his own cold weather bag. A Big Agnes sleeping bag that has built in sleeve for a sleeping pad, so they little ones can't roll of their pads. I'm interested to see how this works out.
Little Red 15°
He absolutely loves camping in the backyard, and used to love riding in the Osprey child carrier but his younger one year old brother has taken that over, and he now has to carry his own weight.
Last year I felt limited with outdoor activities with the little ones because we were not equipped for the cold. They, and we, lacked quality cold weather outdoor clothing, and equipment. Santa is remedying that as well, and I'm hoping all four of us (me, wife, 3 year old, one year old ) will be doing a lot more camping and outdoor activities after the holidays.
... also just to add, we use a Gazelle T4 tent. So far this thing has been amazing. I love how quick it is to set up, especially when my sons so excited about getting in it, and running around. I couldn't imagine the stress of putting poles together and setting up a tent with little kids running around too.