We've been camping with 2 toddlers, and 2 adults, in a 3 person tent. And my sister camped quite a bit with her partner and toddler in a 2 person tent - they used to go by train with it. It's Ok if the weather's good and you can sit and cook outside. We're planning to go camping across Spain with 2 small tents and 2 adults 3 children.
warm sleeping bags, small stove, good waterproof clothes so you don't get everything wet. It's perfectly possible to camp without all the paraphenalia.
but we only go if the weather forecast is good, if it's rainy we cancel.