Explain to kids that the movie was not filmed in 3D and is only being shown in 3D in order to charge you an extra $5 a ticket. I saw it in 2D, and let me tell you, it looked terrific.
While over at Salon, Mary Williams has written an article "I hate 3D":
The 3-D effects in "Avatar" are proof of the indisputably superior potential of the form -- James Cameron managed to pack a lot of breathtaking images in a fairly unobtrusive way. So unobtrusive, in fact, I could have done just fine without any of it