I had mixed feelings about the balloons, I knew they were necessary and I wanted real balloons but the fact they were not edible bothered me, so I am glad you enjoyed them.
I have to say, during the auction, the house was presented by carrying it around the room so people could see it up close. The way the balloons moved made it really feel like it was flying around the room suspended from them... I found great satisfaction in the visual, even though the balloons were not edible.
I also like how the movie paired up with the idea behind Big Brothers, Big Sisters with Carl stepping up at the end to be there for Russell.