At Wilderness last year, we saw a family with a full sized 12+foot Canadian canoe on a dolly.
They had about 5 kids in it, plus all their chairs, jackets, bags etc and dragged it around the festival site all weekend. Looked like a great solution!
Alternatively, a Thule Chariot, or Burley equivalent are very robust, provide good shelter, able to carry lots of weight, comfortable, manoeuvrable and pack down small for the car.
Expensive, but they hold their price very well so you shouldn't lose much of you buy used and sell on again.