Here's a way to look at this:
If there is something that would make a visit personally better for your family, something that they could change that would make it more enjoyable? Safer? Cleaner? More affordable? You'd like to see it happen - even if the experience in the parks overall is still overwhelmingly positive for you. Because not only would you have an even better time, but making something better means they aren't allowing it go get worse (sounds wierd to type that, but doing nothing about a problem usually doesn't result a problem staying static - it tends to get worse).
With access to an audience who wants to learn about WDW... while keeping the overall tone positive, working in some constructive critisism. Encourage guests to enjoy the parks, either as a first timer or as a repeat. But put a bug in their ear that it can be a little better and if they make that improvement the second trip will be better than the first. And that there are ways that a guest can express their desire for something to be improved so the 2nd trip is better than the 1st.
And if others who provide a 'overwhelmingly positive' view on the net get on the act and do the same (esp. if it's co-ordinated around something specific, like say, cleanliness), that's a huge incentive for them to act on it...