DH and I went to an 8pm showing of The Hobbit last night, and a couple had bought their 5-6 yo child, along with her helium balloon.
We were two rows behind, so were only a little distracted by it bobbing around. However the ladies right behind had to ask them to keep it down at least 3 times as they couldn't see.
Whether or not The Hobbit is suitable for that age is another topic for another day...