Initially I was surprised when my 7 year old wanted to see this instead of "Museum" (he has a big brother and the two of them had been talking about the other movie.)
We both loved "Up." Yes, he too was sad when Ellie dies (I got teary) but he laughed out loud and cheered when the good guys won. I think the only thing I would change would be (SPOILER ALERT) the fate of the bad guy. It was disturbing to see him fall, no matter how evil he is made out to be. It would have been easy to make it ambiguous.